toshiba_acpi: Transflective backlight updates

This patch changes the tr function second parameter from bool to u32,
to be on par with the rest of the TCI functions of the driver, and the
code was updated accordingly.

Also, the check for translective support was moved to the *add
function, as the {__get, set}_lcd_brightness functions make use of it.

Signed-off-by: Azael Avalos <coproscefalo@gmail.com>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>