[media] ir-core: fix gcc-7 warning on bool arithmetic

gcc-7 suggests that an expression using a bitwise not and a bitmask
on a 'bool' variable is better written using boolean logic:

drivers/media/rc/imon.c: In function 'imon_incoming_scancode':
drivers/media/rc/imon.c:1725:22: error: '~' on a boolean expression [-Werror=bool-operation]
    ictx->pad_mouse = ~(ictx->pad_mouse) & 0x1;
                      ^
drivers/media/rc/imon.c:1725:22: note: did you mean to use logical not?

I agree.

Fixes: 21677cfc ("V4L/DVB: ir-core: add imon driver")

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>