arch/powerpc/include/asm/fsldma.h needs slab.h

arch/powerpc/include/asm/fsldma.h needs slab.h

The slab.h header is required to use the kmalloc() family of functions.
Due to recent kernel changes, this header must be directly included by
code that calls into the memory allocator.

Without this patch, any code which includes this header fails to build.

Signed-off-by: Ira W. Snyder <iws@ovro.caltech.edu>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>