mx5/6: Fix cpu_mmc_init() return value

Do not pretend to have initialized mmc successfully if CONFIG_FSL_ESDHC is not
defined. Instead, only implement a custom cpu_mmc_init() when it does something.

Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>
Cc: Stefano Babic <sbabic@denx.de>
Acked-by: Stefano Babic <sbabic@denx.de>

arch/arm/cpu/armv7/imx-common/cpu.c

@@ -111,18 +111,16 @@ int cpu_eth_init(bd_t *bis)
 	return rc;
 }
 
+#ifdef CONFIG_FSL_ESDHC
 /*
  * Initializes on-chip MMC controllers.
  * to override, implement board_mmc_init()
  */
 int cpu_mmc_init(bd_t *bis)
 {
-#ifdef CONFIG_FSL_ESDHC
 	return fsl_esdhc_mmc_init(bis);
-#else
-	return 0;
-#endif
 }
+#endif
 
 void reset_cpu(ulong addr)
 {