[POWERPC] Enable GENERIC_ISA_DMA if FSL_ULI1575 to fix compile issue

Since the ULI1575 has a ISA bus we need to enable the generic ISA dma
support for drivers that might expect it.  Without this we get compile
errors like the following:

ound/built-in.o: In function `claim_dma_lock':
/home/galak/git/linux-8572/include/asm/dma.h:189: undefined reference to `dma_spin_lock'
/home/galak/git/linux-8572/include/asm/dma.h:189: undefined reference to `dma_spin_lock'
sound/built-in.o: In function `release_dma_lock':
/home/galak/git/linux-8572/include/asm/dma.h:195: undefined reference to `dma_spin_lock'
sound/built-in.o: In function `claim_dma_lock':
/home/galak/git/linux-8572/include/asm/dma.h:189: undefined reference to `dma_spin_lock'
/home/galak/git/linux-8572/include/asm/dma.h:189: undefined reference to `dma_spin_lock'
sound/built-in.o:/home/galak/git/linux-8572/include/asm/dma.h:195: more undefined references to `dma_spin_lock' follow
make: *** [.tmp_vmlinux1] Error 1

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>