starqltechn: use button keyboard driver

Button keyboard driver used to navigate bootmenu entries.

Add gpio buttons, button keyboard driver.
Add gpio keys dts bindings.

Signed-off-by: Dzmitry Sankouski <dsankouski@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/include/configs/sdm845.h b/include/configs/sdm845.h
index 2211751..673268d 100644
--- a/include/configs/sdm845.h
+++ b/include/configs/sdm845.h
@@ -16,7 +16,7 @@
 #define CFG_EXTRA_ENV_SETTINGS \
 	"bootm_size=0x4000000\0"	\
 	"bootm_low=0x80000000\0"	\
-	"stdin=serial\0"	\
+	"stdin=serial,button-kbd\0"	\
 	"stdout=serial,vidconsole\0"	\
 	"stderr=serial,vidconsole\0"	\
 	"preboot=source $prevbl_initrd_start_addr:prebootscript\0" \