board/orangepi/orangepi-5-plus: fix genimage.cfg

At the moment, Buildroot provides genimage v18. However that version
does not yet include the GUID shortcut for 'u-boot-env' partition type.
This convenient change is relatively new (see [1]) and can be expected
in v19. For now, use the GUID value directly.

[1] https://github.com/pengutronix/genimage/commit/3e0a2aea8d10431f8c8f652129f73544cfa16af2

Fixes: 057012eb2c2c ("configs/orangepi_5_plus: new board")

Signed-off-by: Sergey Matyukevich <geomatsi@gmail.com>
Signed-off-by: Julien Olivain <ju.o@free.fr>

board/orangepi/orangepi-5-plus/genimage.cfg

@@ -10,7 +10,7 @@ image sdcard.img {
 	}
 
 	partition uboot-env {
-		partition-type-uuid = u-boot-env
+		partition-type-uuid = 3de21764-95bd-54bd-a5c3-4abe786f38a8
 		offset = 16M
 		size = 64K
 	}