Input: raspberrypi-ts - select CONFIG_INPUT_POLLDEV

When CONFIG_INPUT_POLLDEV is disabled, we get a link error:

drivers/input/touchscreen/raspberrypi-ts.o: In function `rpi_ts_probe':
raspberrypi-ts.c:(.text+0xec): undefined reference to `devm_input_allocate_polled_device'
raspberrypi-ts.c:(.text+0xec): relocation truncated to fit: R_AARCH64_CALL26 against undefined symbol `devm_input_allocate_polled_device'
raspberrypi-ts.c:(.text+0x19c): undefined reference to `input_register_polled_device'
raspberrypi-ts.c:(.text+0x19c): relocation truncated to fit: R_AARCH64_CALL26 against undefined symbol `input_register_polled_device'

Select that symbol like we do from the other similar drivers.

Fixes: 0b9f28fe ("Input: add official Raspberry Pi's touchscreen driver")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>