Fixes the following W=1 kernel build warning(s):

 drivers/input/touchscreen/surface3_spi.c: In function ‘surface3_spi_process_touch’:
 drivers/input/touchscreen/surface3_spi.c:97:6: warning: variable ‘timestamp’ set but not used [-Wunused-but-set-variable]
 drivers/input/touchscreen/surface3_spi.c:225: warning: Function parameter or member 'data' not described in 'surface3_spi_get_gpio_config'
 drivers/input/touchscreen/surface3_spi.c:225: warning: Excess function parameter 'ts' description in 'surface3_spi_get_gpio_config'
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20201112110204.2083435-11-lee.jones@linaro.orgSigned-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>