For 64-bit BAR[i] only pci_dev->resource[i] is valid, ->resource[i+1]
slot is unused and contains zeroes in all fields.

So when we update a PCI BAR, all we need is just to check that we're
going to update a _valid_ resource.

Also make sure to write high bits - use "x >> 16 >> 16" (rather than the
simpler ">> 32") to avoid warnings on 32-bit architectures where we're
not going to have any high bits.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>