mx6slevk: Fix unused variable warning

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

Cc: Fabio Estevam <fabio.estevam@nxp.com>
Cc: Peng Fan <peng.fan@nxp.com>
Cc: Stefano Babic <sbabic@denx.de>
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/mx6slevk/mx6slevk.c

@@ -66,6 +66,7 @@ static iomux_v3_cfg_t const uart1_pads[] = {
 	MX6_PAD_UART1_RXD__UART1_RXD | MUX_PAD_CTRL(UART_PAD_CTRL),
 };
 
+#ifdef CONFIG_SPL_BUILD
 static iomux_v3_cfg_t const usdhc1_pads[] = {
 	/* 8 bit SD */
 	MX6_PAD_SD1_CLK__USDHC1_CLK | MUX_PAD_CTRL(USDHC_PAD_CTRL),
@@ -106,6 +107,7 @@ static iomux_v3_cfg_t const usdhc3_pads[] = {
 	/*CD pin*/
 	MX6_PAD_REF_CLK_32K__GPIO_3_22 | MUX_PAD_CTRL(NO_PAD_CTRL),
 };
+#endif
 
 static iomux_v3_cfg_t const fec_pads[] = {
 	MX6_PAD_FEC_MDC__FEC_MDC | MUX_PAD_CTRL(ENET_PAD_CTRL),