ARM: dts: msm: Add reservation for framebuffer memory

The framebuffer needs contiguous memory to work. Add a
dedicated CMA region for framebuffer. This region is
specified with a default size which works for most targets
and overridden for targets that have a larger screen and
therefore require a large framebuffer.

Change-Id: If5f23884f6779ed325be15ee2e16e3bd23ba3698
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>