msm: board-8064: Increase MFC ION heap size by 256KB

In order to support extra data during secure playback,
video core meta data buffers need to be allocated from
MFC heap. This is required as both HLOS and video core
have read-write access to this heap. As each meta buffer
size is 8KB and there can be 32 meta & output buffers,
increase the MFC ION heap size by  256KB.

Change-Id: I033d24c9d02a879e38c5f6d86b2b6c0a767ec25c
Signed-off-by: Deepak Verma <dverma@codeaurora.org>