drivers: input: ft5336: Enable interrupts in conjunction with DT config

Enabling `CONFIG_INPUT_FT5336_INTERRUPT` if the ft5336 node in DT
has `int-gpios` property.

As a result of this change, some boards can eliminate lines that
explicitly configure `CONFIG_INPUT_FT5336_INTERRUPT`.

Signed-off-by: TOKITA Hiroshi <tokita.hiroshi@gmail.com>