[PATCH] powerpc: Fix GENERIC_ISA_DMA dependency

[Liu Dave-R63238]

> On PowerPC we should always use generic ISA DMA API implementation
> as there is simply no other implementation exist.
> 
> Without this patch, the following build error pops up:
> 
>   sound/built-in.o: In function 'snd_dma_pointer':
>   (.text+0x74ae): undefined reference to 'dma_spin_lock'
>   ...
>   make: *** [.tmp_vmlinux1] Error 1
> 
> This is PPC_85xx, SMP and some sound drivers set to =y.
> 
> Signed-off-by: Anton Vorontsov <avorontsov at mvista.com>

Acked-by: Dave Liu <daveliu at freescale.com>

I happened this issue when I developed P1022DS BSP.