Input: ti_am335x_tsc - remove set but not used variable 'tscadc_dev'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/input/touchscreen/ti_am335x_tsc.c: In function 'titsc_suspend':
drivers/input/touchscreen/ti_am335x_tsc.c:510:24: warning:
 variable 'tscadc_dev' set but not used [-Wunused-but-set-variable]

drivers/input/touchscreen/ti_am335x_tsc.c: In function 'titsc_resume':
drivers/input/touchscreen/ti_am335x_tsc.c:527:24: warning:
 variable 'tscadc_dev' set but not used [-Wunused-but-set-variable]

It's not used any more after 333e07ec

 ("Input: ti_am335x_tsc: Mark TSC
device as wakeup source")

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