libata calls pci_request_regions to claim PCI BAR 0 - 5
pci_request_regions fails if one of the regions cant be claimed.
bar 5 has start == 0,  __request_resource will fail.

Tested on a p630 in SMP mode with pata_sl82c105

 00:03.1 IDE interface: Symphony Labs SL82c105 (rev 05) (prog-if 8f [Master SecP SecO PriP PriO])
         Control: I/O+ Mem- BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr+ Stepping- SERR+ FastB2B-
         Status: Cap- 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR-
         Interrupt: pin A routed to IRQ 86
         Region 0: I/O ports at 3fd3000f000 [size=8]
         Region 1: I/O ports at 3fd3000f010 [size=4]
         Region 2: I/O ports at 3fd3000f020 [size=8]
         Region 3: I/O ports at 3fd3000f030 [size=4]
         Region 4: I/O ports at 3fd3000f040 [size=16]
         Region 5: I/O ports at 3fd30000000 [size=16]
 00: ad 10 05 01 41 01 80 02 05 8f 01 01 08 48 80 00
 10: 01 f0 00 00 11 f0 00 00 21 f0 00 00 31 f0 00 00
 20: 41 f0 00 00 01 00 00 00 00 00 00 00 00 00 00 00
 30: 00 00 00 00 00 00 00 00 00 00 00 00 56 01 02 28
 40: b3 08 ff 00 09 09 00 00 09 09 00 00 09 09 00 00
 50: 09 09 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 60: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 70: 00 00 00 00 00 00 00 00 00 00 00 00 ff 00 00 00
 80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

 name             "ide"
 linux,phandle    00d5cdc0 (14011840)
 assigned-addresses 81001910 00000000 0000f000 00000000 00000008 81001914
                  00000000 0000f010 00000000 00000004 81001918 00000000
                  0000f020 00000000 00000008 8100191c 00000000 0000f030
                  00000000 00000004 81001920 00000000 0000f040 00000000
                  00000010 81001924 00000000 00000000 00000000 00000010
 interrupts       00000003
 built-in
 #size-cells      00000000
 #address-cells   00000001
 device_type      "ide"
 reg              00001900 00000000 00000000 00000000 00000000
                  41001910 00000000 00000000 00000000 00000008
                  41001914 00000000 00000000 00000000 00000004
                  41001918 00000000 00000000 00000000 00000008
                  4100191c 00000000 00000000 00000000 00000004
                  41001920 00000000 00000000 00000000 00000010
                  41001924 00000000 00000000 00000000 00000010
 compatible       "pci10ad,105"
                  "pciclass,01018f"
 ibm,fw-slot-number 00000000
 fast-back-to-back
 devsel-speed     00000001
 max-latency      00000028 (40)
 min-grant        00000002
 class-code       0001018f (65935)
 revision-id      00000005
 device-id        00000105 (261)
 vendor-id        000010ad (4269)
 ibm,loc-code     "U0.1-P1/Q6"
Signed-off-by: Olaf Hering <olaf@aepfle.de>
Signed-off-by: Paul Mackerras <paulus@samba.org>