msm: kgsl: Fix searching of memory object

Make sure that at least a size of 1 byte is searched when locating
the memory entry of a region. If size is 0 then a memory region
whose last address is equal to the start address of the memory being
searched will be returned which is wrong.

Change-Id: I643185d1fdd17296bd70fea483aa3c365e691bc5
Signed-off-by: Shubhraprakash Das <sadas@codeaurora.org>