Input: mt - cleanup open-coded __set_bit()

Replace open-coded __set_bit() with the function.

Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Link: https://lore.kernel.org/r/cf1dda3a372896cb01033ce084a7deb9620df7aa.1594599118.git.mirq-linux@rere.qmqm.pl


Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>