msm: rotator: add check for buffers boundaries

check that offset is within the range of buffer to avoid possible
access to other memory regions.

Change-Id: I37f49b0c95cc9bf79a09c7b0fa04f1135b691a5d
CRs-Fixed: 308058
Signed-off-by: Adrian Salido-Moreno <adrianm@codeaurora.org>