mxcfb.h: update mxc header file to include new temperature ioctls

The ioctls are used to get/set the temperature used by the mxc ePDC
driver.

Signed-off-by: Andrew Cox <andrew.cox@plasticlogic.com>
Makefile: use immediate variable assignment operator
linux/pmeter.h: update with user-side functions
ChangeLog v1.5 -> v1.6