fsl_esdhc: Initialize mmc->b_max

commit 262951(MMC: make b_max unconditional) missed to update fsl_esdhc.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Stefano Babic <sbabic@denx.de>
diff --git a/drivers/mmc/fsl_esdhc.c b/drivers/mmc/fsl_esdhc.c
index d2355be..ec953f0 100644
--- a/drivers/mmc/fsl_esdhc.c
+++ b/drivers/mmc/fsl_esdhc.c
@@ -525,6 +525,7 @@
 	mmc->f_min = 400000;
 	mmc->f_max = MIN(gd->sdhc_clk, 52000000);
 
+	mmc->b_max = 0;
 	mmc_register(mmc);
 
 	return 0;