staging: omap-thermal: refactor temp_sensor_unmask_interrupts

This change improves temp_sensor_unmask_interrupts by:
. renaming it to omap_bandgap_unmask_interrupts
. making it a void function, as there is nothing really to report an error.

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