Input: qt2160 - rename kconfig symbol name

drivers/input/keyboard/Kconfig defines QT2160 while the corresponding
Makefile expects CONFIG_KEYBOARD_QT2160 as all other keyboard drivers
do. To keep this Makefile consistent rename the config-token from
CONFIG_QT2160 to CONFIG_KEYBOARD_QT2160.

The various defconfig files are left alone.

Reported-by: Robert P. J. Day <rpjday@crashcourse.ca>
Signed-off-by: Christoph Fritz <chf.fritz@googlemail.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>