Input: soc_button_array - add missing include

This fixes the following build errors:

  CC [M]  drivers/input/misc/soc_button_array.o
drivers/input/misc/soc_button_array.c:156:4: error: implicit declaration of function 'irq_set_irq_type' [-Werror,-Wimplicit-function-declaration]
                        irq_set_irq_type(irq, IRQ_TYPE_LEVEL_LOW);
                        ^
drivers/input/misc/soc_button_array.c:156:26: error: use of undeclared identifier 'IRQ_TYPE_LEVEL_LOW'
                        irq_set_irq_type(irq, IRQ_TYPE_LEVEL_LOW);
                                              ^
2 errors generated.

Fixes: 78a5b53e

 ("Input: soc_button_array - work around DSDTs which modify the irqflags")
Reported-by: kernel test robot <lkp@intel.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20201123061508.GA1009828@dtor-ws
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>