input: samsung-keypad: Add HAVE_SAMSUNG_KEYPAD config option

input: samsung-keypad: Add HAVE_SAMSUNG_KEYPAD config option

For platforms using device tree, the static keypad device instances
are not required and SAMSUNG_DEV_KEYPAD is not selected. Since,
samsung keypad driver has dependency on SAMSUNG_DEV_KEYPAD config
option, the driver is left out of the compilation for dt enabled
platforms.

An additional config option 'HAVE_SAMSUNG_KEYPAD' is added
which the device tree based platforms can select. This config
option is added as an alternative dependency for keypad driver.

Signed-off-by: Thomas Abraham <thomas.abraham@linaro.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>