msm: camera: Use correct type for function return code

Using an unsigned integer to hold the signed return code
is wrong. So fix it by using the correct type to hold the
return code.

CRs-fixed: 512824
Change-Id: I389732a9af740174b26c8c43946e638a1be0d2a2
Signed-off-by: Seemanta Dutta <seemanta@codeaurora.org>