Fix compilation with GCC 4.8

GCC 4.8 barfs when trying to find the calls in hwc_fbupdate.cpp
to functions defined in hwc_utils.h and defed inlined in hwc_utils.cpp

Change-Id: I74433b1125fedd528138e00175849765dd0f6349
Signed-off-by: nuclearmistake <nuclearmistake@gmail.com>