ARM: mmp: add sram allocator

On mmp platform, there have two sram banks:
audio sram and internal sram. The audio sram is mainly for audio;
the internal sram is for video, wtm and power management.
So add the sram allocator using genalloc to manage them.

Every sram bank will register its own platform device
info, after the sram allocator create the generic pool
for the sram bank, the user module can use the pool's
name to get the pool handler; then it can use the handler
to alloc/free memory with genalloc APIs.

Signed-off-by: Leo Yan <leoy@marvell.com>
Acked-by: Haojian Zhuang <haojian.zhuang@gmail.com>
Signed-off-by: Eric Miao <eric.y.miao@gmail.com>