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

Follow Documentation/CodingStyle while doing  omap_bandgap_adc_to_mcelsius.

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