ath79: disable building future NAND images for GL-AR300M/GL-AR750S

To simplify the upgrade process and ensure easier identification of
device partitioning, the following devices are disabled on ath79
target in openwrt-19.07 branch:

- glinet,gl-ar300m-nor
- glinet,gl-ar300m-nand
- glinet,gl-ar750s

Proper ath79 (NAND) support for the devices is expected to be
introduced based on kernel 4.19 (see GitHub PR #2184).

In openwrt-19.07, ar71xx should be used for those devices.

With this, we ensure that the new ath79 image names (at least for
releases) refer to the updated partitioning.

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>

target/linux/ath79/image/generic.mk

@@ -395,7 +395,7 @@ define Device/glinet_gl-ar300m-nor
   $(Device/glinet_gl-ar300m-common-nor)
   DEVICE_TITLE := GL.iNet GL-AR300M
 endef
-TARGET_DEVICES += glinet_gl-ar300m-nor
+#TARGET_DEVICES += glinet_gl-ar300m-nor
 
 define Device/glinet_gl-ar750s
   ATH_SOC := qca9563
@@ -404,7 +404,7 @@ define Device/glinet_gl-ar750s
   IMAGE_SIZE := 16000k
   SUPPORTED_DEVICES += gl-ar750s
 endef
-TARGET_DEVICES += glinet_gl-ar750s
+#TARGET_DEVICES += glinet_gl-ar750s
 
 define Device/glinet_gl-x750
   ATH_SOC := qca9531

target/linux/ath79/image/nand.mk

@@ -10,4 +10,4 @@ define Device/glinet_gl-ar300m-nand
   IMAGE/sysupgrade.bin := sysupgrade-tar
   IMAGE/factory.ubi := append-kernel | pad-to $$$$(KERNEL_SIZE) | append-ubi
 endef
-TARGET_DEVICES += glinet_gl-ar300m-nand
+#TARGET_DEVICES += glinet_gl-ar300m-nand