samples: basic: button: Rework to not define generated macros
samples: basic: button: Rework to not define generated macros

Rather than redefining a macro which might be generated we should create
a new define name that should get used in the code.  Replace redefining
DT_ALIAS_SW0_GPIOS_FLAGS with SW0_FLAGS and DT_ALIAS_LED0_GPIOS_FLAGS
with LED0_FLAGS.

Signed-off-by: Kumar Gala <a5e5248af4cd4f0ed8c515f61d40a6e2db46a66e@linaro.org>

finikorg/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,finikorg/zephyr,galak/zephyr,nashif/zephyr,Vudentz/zephyr,nashif/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,finikorg/zephyr,nashif/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,Vudentz/zephyr,Vudentz/zephyr,finikorg/zephyr,nashif/zephyr,galak/zephyr,Vudentz/zephyr