staging: omap-thermal: create header for register, bitfields and definitions

In order to have a better code readability and organization, this patch
splits omap-bandgap.h into three headers.
. omap-bandgap.h will contain only the driver related data structures
definitions and macros
. omap4xxx-bandgap.h will contain only defines and bitfields
related to OMAP4 based devices
. omap5xxx-bandgap.h will contain only defines and bitfields
related to OMAP5 based devices

Signed-off-by: Eduardo Valentin <eduardo.valentin@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>