board: mscc: serval: Fix board detect

When detecting the board, it was reading a register in the GPIO page of
the phy and based on that value it was making a decision. The bug was that
after the GPIO page for the first phy was set it was not reseted back.

Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
diff --git a/board/mscc/serval/serval.c b/board/mscc/serval/serval.c
index 24ee5e5..ade041e 100644
--- a/board/mscc/serval/serval.c
+++ b/board/mscc/serval/serval.c
@@ -42,10 +42,10 @@
 			gd->board_type = BOARD_TYPE_PCB106;
 		else
 			gd->board_type = BOARD_TYPE_PCB105;
-		mscc_phy_wr(1, 16, 15, 0);
 	} else {
 		gd->board_type = BOARD_TYPE_PCB105;
 	}
+	mscc_phy_wr(1, 16, 31, 0x0);
 }
 
 #if defined(CONFIG_MULTI_DTB_FIT)