ath79: Clean up GL-AR300M DTS/DTSI inclusions

Modify GL-AR300M-Lite and GL-AR300M (NOR):

* Include qca9531_glinet_gl-ar300m.dtsi directly
  rather than qca9531_glinet_gl-ar300m-nor.dts

* Remove redundant inclusion of gpio.h and input.h

Signed-off-by: Jeff Kletsky <git-commits@allycomm.com>
Reviewed-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
(cherry picked from commit f5c7fe2ff0deb20f76b4d65195434e35cbb4e08a)