mvebu: fix default partition name

The firmware partition name is specifc to ipTIME NAS1dual and should not be
set globally.

Fixes: #16148
Fixes: 6ff970bb51 ("mvebu: add support for ipTIME NAS1dual")
Signed-off-by: Boris Krasnovskiy <borkra@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/16690
Signed-off-by: Robert Marko <robimarko@gmail.com>

target/linux/mvebu/cortexa9/base-files/lib/upgrade/platform.sh

@@ -6,7 +6,6 @@
 RAMFS_COPY_BIN='fw_printenv fw_setenv seq strings'
 RAMFS_COPY_DATA='/etc/fw_env.config /var/lock/fw_printenv.lock'
 
-PART_NAME=firmware
 REQUIRE_IMAGE_METADATA=1
 
 platform_check_image() {
@@ -74,6 +73,10 @@ platform_do_upgrade() {
 		esac
 		default_do_upgrade "$1"
 		;;
+	iptime,nas1dual)
+		PART_NAME=firmware
+		;;
+
 	linksys,wrt1200ac|\
 	linksys,wrt1900ac-v1|\
 	linksys,wrt1900ac-v2|\