samples: button: set EDGE to SW0_GPIO_INT_CONF if defined

SW0_GPIO_INT_CONF shall allow boards to define the
interrupt configuration for SW0 without having to modify
the button sample app.

If SW0_GPIO_INT_CONF is defined set EDGE to it, otherwise
used default EDGE value.

Change-Id: Ia697e06debc341463ed9cdee1db564f3727d27e3
Signed-off-by: Jean-Paul Etienne <fractalclone@gmail.com>
1 file changed