msm: camera: Restructure data handling to be more robust

Use dynamic array allocation instead of static array to
prevent stack overflow.
User-supplied number of bytes may result in integer overflow.
To fix this we check that the num_byte isn't above 8K size.

CRs-Fixed: 1060554
Change-Id: I407b5ec8cdc2ac7f3b491644418d3eb1101ce65a
Signed-off-by: Samyukta Mogily <smogily@codeaurora.org>