Add 'poker' target to Makefile.pjrc of gh60

keyboard/gh60/Makefile.pjrc

@@ -89,5 +89,8 @@ include $(TOP_DIR)/protocol/pjrc.mk
 include $(TOP_DIR)/common.mk
 include $(TOP_DIR)/rules.mk
 
-plain: OPT_DEFS += -DPLAIN_MAP
+plain: OPT_DEFS += -DKEYMAP_PLAIN
 plain: all
+
+poker: OPT_DEFS += -DKEYMAP_POKER
+poker: all