vt: keyboard, use find_next_bit in kbd_match

Instead of a 'for' loop with 'test_bit's to find a bit in a range, use
find_next_bit to achieve the same in a simpler and faster manner.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20201029113222.32640-16-jslaby@suse.cz


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>