mx6ul_14x14_evk: Fix unused variable warning

The variable usdhc1_pads is only referenced during SPL builds, add a guard.

Cc: Stefano Babic <sbabic@denx.de>
Cc: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Stefano Babic <sbabic@denx.de>

board/freescale/mx6ul_14x14_evk/mx6ul_14x14_evk.c

@@ -225,6 +225,7 @@ static iomux_v3_cfg_t const uart1_pads[] = {
 	MX6_PAD_UART1_RX_DATA__UART1_DCE_RX | MUX_PAD_CTRL(UART_PAD_CTRL),
 };
 
+#ifndef CONFIG_SPL_BUILD
 static iomux_v3_cfg_t const usdhc1_pads[] = {
 	MX6_PAD_SD1_CLK__USDHC1_CLK | MUX_PAD_CTRL(USDHC_PAD_CTRL),
 	MX6_PAD_SD1_CMD__USDHC1_CMD | MUX_PAD_CTRL(USDHC_PAD_CTRL),
@@ -240,6 +241,7 @@ static iomux_v3_cfg_t const usdhc1_pads[] = {
 	/* RST_B */
 	MX6_PAD_GPIO1_IO09__GPIO1_IO09 | MUX_PAD_CTRL(NO_PAD_CTRL),
 };
+#endif
 
 /*
  * mx6ul_14x14_evk board default supports sd card. If want to use