mediatek: Fix U-Boot variables handling for D-Link M30 A1

I think I implemented the U-Boot handling incorrectly on M30 (saw the issue while porting M60 to OpenWrt). Maybe someone with more U-Boot experience can have a look at it.
What I understood until now:

Before flashing, `sw_tryactive` must be set to 0 because OpenWrt runs on partition 0

During reset after flashing, U-Boot executes the following line:
`boot_rd_auto_sw_img=if itest.s ${sw_tryactive} == 2; then run boot_by_part; else run boot_by_tryactive; fi`

As `sw_tryactive` was set to 0 before flashing, `boot_by_tryactive` will be executed:
`boot_by_tryactive=if itest.s ${sw_tryactive} == 0; then setenv sw_tryactive 2; setenv sw_active 1; saveenv; run ub0; else setenv sw_tryactive 2; setenv sw_active 2; saveenv; run ub1; fi`

As `sw_tryactive` was set to 0 before flashing, `sw_active` will be set to 1 and `ub0` will be executed:
`ub0=setenv bootpart 0; mtkboardboot; run ub0to1; uip main; reset`

If the OpenWrt boot is successful, `ub0to1` and `uip` main will never be executed. Only in case OpenWrt cannot be loaded, `mtkboardboot` will return and the fallback `ub0to1` is executed.

Conclusion: It's sufficient to set `sw_tryacitve` to 0 before flashing, the added code in `target/linux/mediatek/filogic/base-files/etc/init.d/bootcount` is useless.
In the worst case (/proc/cmdline doesn't contain `bootpart=ubi0` as expected), the bootpart variable would be set to 1 and causes starting the firmware from the second partition instead of the one on the first partition.

Signed-off-by: Roland Reinl <[email protected]>
Link: openwrt/openwrt#17298
Signed-off-by: Hauke Mehrtens <[email protected]>

target/linux/mediatek/filogic/base-files/etc/init.d/bootcount

@@ -5,13 +5,6 @@ START=99
 
 boot() {
 	case $(board_name) in
-	dlink,aquila-pro-ai-m30-a1)
-		if grep -q bootpart=ubi0 /proc/cmdline; then
-			fw_setenv bootpart 0
-		else
-			fw_setenv bootpart 1
-		fi
-		;;
 	zyxel,ex5700-telenor)
 		fw_setenv uboot_bootcount 0
 		;;

target/linux/mediatek/filogic/base-files/lib/upgrade/platform.sh

@@ -123,6 +123,7 @@ platform_do_upgrade() {
 	yuncore,ax835)
 		default_do_upgrade "$1"
 		;;
+	dlink,aquila-pro-ai-m30-a1|\
 	dlink,aquila-pro-ai-m60-a1)
 		fw_setenv sw_tryactive 0
 		nand_do_upgrade "$1"