ARM: dts: Add scratch buffer support as a device tree parameter

Some camera context banks may need support for scratch buffer support.
So introduce this support via an optional device tree parameter in the
corresponding device tree node for that context bank.

Change-Id: Id3e712f67efd53ab3cf27caddef19749290fc2a5
Signed-off-by: Seemanta Dutta <seemanta@codeaurora.org>