samples: buttons: Add GPIO_INT_EDGE to button configuration
samples: buttons: Add GPIO_INT_EDGE to button configuration

Add GPIO_INT_EDGE triggering for the button push for boards where
the dts generates a SW0_GPIO_FLAGS.

Signed-off-by: David Leach <98707a1e43c521c5b5b81e36afef696dde6831a3@nxp.com>

ldts/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,explora26/zephyr,Vudentz/zephyr,Vudentz/zephyr,explora26/zephyr,ldts/zephyr,ldts/zephyr,explora26/zephyr,galak/zephyr,ldts/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,punitvara/zephyr,punitvara/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,nashif/zephyr,Vudentz/zephyr,finikorg/zephyr,ldts/zephyr,GiulianoFranchetto/zephyr,explora26/zephyr,galak/zephyr,finikorg/zephyr,punitvara/zephyr,punitvara/zephyr,Vudentz/zephyr,nashif/zephyr,Vudentz/zephyr,punitvara/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,explora26/zephyr,nashif/zephyr,nashif/zephyr