ath79-nand: fix upgrade from 19.07 for GL-AR300M (#2641)

Support for the device was (re)added in #2455
(merged as 94e04393)

(cherry picked from commit cd37fe5d60543a0af296f64880ca7047c681a82a)

Co-authored-by: Tom Herbers <mail@tomherbers.de>

targets/ath79-nand

@@ -11,6 +11,9 @@ local ATH10K_PACKAGES_QCA9887 = {
 
 device('gl.inet-gl-ar300m-nor', 'glinet_gl-ar300m-nor', {
 	factory = false,
+	manifest_aliases = {
+		'gl.inet-gl-ar300m', -- Upgrade from OpenWrt 19.07
+	},
 })
 
 device('gl.inet-gl-ar750s-nor', 'glinet_gl-ar750s-nor', {