The temperature calculation currently uses fixed point operations.
Change it to use floating point for better readability and maintenance.
Also changes disable_fpu() to accept parameter which serves as
optimization barrier to prevent floating point operations after
disabling FPU.
BUG=chrome-os-partner:7801
TEST=In console, tempremote "tempremote 29715 -105000 6390" gives 28506.
Change-Id: Ib766904b8feb9a78eac9f7cd53afeca85091c5a5
Signed-off-by: Vic Yang <victoryang@chromium.org>