mxc: Fix SDHC multi-instance clock

On mxc, each SDHC instance has a dedicated clock, so gd->sdhc_clk is not
suitable for the multi-instance use case (initialization made directly with
fsl_esdhc_initialize()).

This patch fixes this issue by adding a configuration field for the SDHC input
clock frequency.

Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Eric Bénard <eric@eukrea.com>
Cc: Otavio Salvador <otavio@ossystems.com.br>
Cc: Fabio Estevam <fabio.estevam@freescale.com>
Cc: Jason Liu <r64343@freescale.com>
Cc: Matt Sealey <matt@genesi-usa.com>
Cc: Andy Fleming <afleming@gmail.com>
diff --git a/board/freescale/mx53loco/mx53loco.c b/board/freescale/mx53loco/mx53loco.c
index 6543209..20569a5 100644
--- a/board/freescale/mx53loco/mx53loco.c
+++ b/board/freescale/mx53loco/mx53loco.c
@@ -192,6 +192,9 @@
 	u32 index;
 	s32 status = 0;
 
+	esdhc_cfg[0].sdhc_clk = mxc_get_clock(MXC_ESDHC_CLK);
+	esdhc_cfg[1].sdhc_clk = mxc_get_clock(MXC_ESDHC3_CLK);
+
 	for (index = 0; index < CONFIG_SYS_FSL_ESDHC_NUM; index++) {
 		switch (index) {
 		case 0: