ARM: AM43xx: GP-EVM: Correct GPIO used for VTT regulator control

Schematic indicates GPIO5_7 is to be used for VTT regulator control
rather than GPIO0_21 so modify enable_vtt_regulator to reflect this.
Without this some boards will experience DDR3 corruption and fail to
boot.

Signed-off-by: Dave Gerlach <d-gerlach@ti.com>
[trini: Rework patch against mainline]
Signed-off-by: Tom Rini <trini@ti.com>
diff --git a/board/ti/am43xx/mux.c b/board/ti/am43xx/mux.c
index 810b194..51f7fd6 100644
--- a/board/ti/am43xx/mux.c
+++ b/board/ti/am43xx/mux.c
@@ -33,8 +33,8 @@
 	{-1},
 };
 
-static struct module_pin_mux gpio0_22_pin_mux[] = {
-	{OFFSET(ddr_ba2), (MODE(9) | PULLUP_EN)},	/* GPIO0_22 */
+static struct module_pin_mux gpio5_7_pin_mux[] = {
+	{OFFSET(spi0_cs0), (MODE(7) | PULLUP_EN)},	/* GPIO5_7 */
 	{-1},
 };
 
@@ -49,7 +49,7 @@
 	configure_module_pin_mux(i2c0_pin_mux);
 
 	if (board_is_gpevm())
-		configure_module_pin_mux(gpio0_22_pin_mux);
+		configure_module_pin_mux(gpio5_7_pin_mux);
 }
 
 void enable_i2c0_pin_mux(void)