msm: camera: isp: change variables declaration to static

Static variables are initialized only once and the compiler
persists with the variable till the end of the program hence
declaring some of the varaibles in header files as static.

CRs-Fixed: 2663712
Change-Id: I55265f5ac1d144ae5b5c62a9984c08d242be157d
Signed-off-by: Vishalsingh Hajeri <vhajeri@codeaurora.org>