staging: omap-thermal: rewrite omap_bandgap_mcelsius_to_adc on kernel coding style

Follow Documentation/CodingStyle while doing omap_bandgap_mcelsius_to_adc

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