Input: qt2160 - tweak check for i2c adapter functionality

i2c_check_functionality() returns essentially a boolean and not an error
code, so treat it as such.

Link: https://lore.kernel.org/r/20230724051345.335219-1-dmitry.torokhov@gmail.com


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