Fix the following build warning when building driver with CONFIG_PM_SLEEP
not selected.

tegra-kbc.c:360:13: warning: 'tegra_kbc_set_keypress_interrupt' defined but not used [-Wunused-function]
Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>