mm-video: venc: use source stride for color-converting RGB input

 -RGB input may be composed by GPU with an aligned stride
  different from the frame-width.
 -CTS test cases testEncodeDecodeVideoFromSurfaceToSurface720p
  and testVideoEdit720p fails because gralloc-handle
  stride value is not used
 -Extract this stride from gralloc-handle to interpret the buffer

Change-Id: I63fd224e933424e1e8c49a19270545f000a2ebd5
mm-video: Use multimedia heap on MSM7x30 (720p) too.

Change-Id: I8c7997a1fdd9490cbec9729b07a50f40b1c07c2b
mm-video: vdec: Fix memory leak in color converter.

When OMX is deinitialized, the color converter buffers stay intact, causing the
available memory pool to have less continuous space available.

Change-Id: Icc2d730d540bae153c9fde36a6f4267ff3f9f088