airoha: set ROOTFS_DATA_ALIGMENT for airoha devices

Defined ROOTFS_DATA_ALIGMENT as 0x00080000 for the airoha devices to
specify the rootfs data alignment used during FIT image generation.
This ensures correct offset calculation when handling rootfs data partitions.

Issue: #16567

airoha/image/Makefile

@@ -8,7 +8,7 @@ include ../../iopsys-common/iopsys-fit-image.mk
 include ../../iopsys-common/iopsys-sign-image.mk
 
 DTS_DIR := ../dts
-DEVICE_VARS += DEVICE_UBI_LAYOUT UBOOT_TARGET GPT_LAYOUT_STR GPT_PRIMARY_ENTRY_OFFSET GPT_ALTERNATE_OFFSET FIT_PARTITION
+DEVICE_VARS += DEVICE_UBI_LAYOUT UBOOT_TARGET GPT_LAYOUT_STR GPT_PRIMARY_ENTRY_OFFSET GPT_ALTERNATE_OFFSET FIT_PARTITION ROOTFS_DATA_ALIGMENT
 
 define airoha-emmc-production
   append_emmc_production_image $(1)
@@ -35,6 +35,7 @@ define Device/Default-airoha-emmc
   ARTIFACT/u-boot-emmc.fip := append-uboot-emmc
   ARTIFACTS := u-boot-emmc.fip u-boot-nand.bin u-boot-recovery.bin u-boot-ram.itb bootext.ram
   IMAGE/production.img := $$(call airoha-emmc-production)
+  ROOTFS_DATA_ALIGMENT := 0x00080000
 endef
 
 define Device/Default-airoha-common