[POWERPC] Don't compile arch/powerpc mpc52xx_pic driver for ARCH=ppc

arch/powerpc/sysdev/mpc52xx_pic.c breaks the ppc build
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/sysdev/Makefile

@@ -11,11 +11,11 @@ obj-$(CONFIG_MMIO_NVRAM)	+= mmio_nvram.o
 obj-$(CONFIG_FSL_SOC)		+= fsl_soc.o
 obj-$(CONFIG_TSI108_BRIDGE)	+= tsi108_pci.o tsi108_dev.o
 obj-$(CONFIG_QUICC_ENGINE)	+= qe_lib/
-obj-$(CONFIG_PPC_MPC52xx)	+= mpc52xx_pic.o
 
 ifeq ($(CONFIG_PPC_MERGE),y)
 obj-$(CONFIG_PPC_I8259)		+= i8259.o
 obj-$(CONFIG_PPC_83xx)		+= ipic.o
+obj-$(CONFIG_PPC_MPC52xx)	+= mpc52xx_pic.o
 endif
 
 # Temporary hack until we have migrated to asm-powerpc