ARM: pxa: Fix build error caused by sram.h rename

Commit 293b2da1 ("ARM: pxa: move platform_data definitions")
renamed arch/arm/mach-mmp/include/mach/sram.h to
include/linux/platform_data/dma-mmp_tdma.h, but didn't update
mmp-pcm.c which uses the header.  Fix the build error.

Signed-off-by: Chris Ball <cjb@laptop.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>