board: purism: librem5: Move the board rev to the MAC address fuses

NXP has changed the layout of the OTP fuses and the user area is no longer
writable so we'll overload the MAC address as a board revision number.
Signed-off-by: Angus Ainslie <angus@akkea.ca>

board/purism/librem5/librem5.c

@@ -568,15 +568,13 @@ int fastboot_key_pressed(void)
 int board_late_init(void)
 {
 #ifdef CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
-	u32 vid, rev;
+	u32 rev;
 	char rev_str[3];
 
 	env_set("board_name", "librem5");
-	if (fuse_read(8, 2, &vid) || fuse_read(14, 0, &rev))
+	if (fuse_read(9, 0, &rev)) {
 		env_set("board_rev", BOARD_REV_ERROR);
-	else if (vid == 0) {
-		env_set("board_rev", BOARD_REV_UNKNOWN);
-	} else if (vid == (PURISM_PID<<16 | PURISM_VID)) {
+	} else {
 		sprintf(rev_str, "%u", rev);
 		env_set("board_rev", rev_str);
 	}