ar71xx: add support for RB750UPr2

This patch adds support for the MikroTik RouterBOARD hEX PoE lite
https://routerboard.com/RB750UPr2

Specifications:
- SoC: Qualcomm QCA9531 (650MHz)
- RAM: 64MB
- Storage: 16MB NOR SPI flash
- Ethernet: 5x100M (1 PoE in, 1 PoE out)
- USB: Type A

This ethernet router is based on the same platform as the wireless router hAP.

Signed-off-by: Thibaut VARENE <hacks@slashdirt.org>

target/linux/ar71xx/base-files/lib/ar71xx.sh

@@ -838,6 +838,9 @@ ar71xx_board_detect() {
 	*"RouterBOARD 750GL")
 		name="rb-750gl"
 		;;
+	*"RouterBOARD 750UP r2")
+		name="rb-750up-r2"
+		;;
 	*"RouterBOARD 751")
 		name="rb-751"
 		;;

target/linux/ar71xx/base-files/lib/upgrade/platform.sh

@@ -343,6 +343,7 @@ platform_check_image() {
 	ls-sr71|\
 	pb42|\
 	pb44|\
+	rb-750up-r2|\
 	rb-941-2nd|\
 	rb-951ui-2nd|\
 	rb-mapl-2nd|\
@@ -617,6 +618,7 @@ platform_pre_upgrade() {
 	local board=$(ar71xx_board_name)
 
 	case "$board" in
+	rb-750up-r2|\
 	rb-941-2nd|\
 	rb-951ui-2nd|\
 	rb-mapl-2nd)
@@ -655,6 +657,7 @@ platform_do_upgrade() {
 	local board=$(ar71xx_board_name)
 
 	case "$board" in
+	rb-750up-r2|\
 	rb-941-2nd|\
 	rb-951ui-2nd|\
 	rb-mapl-2nd)