Revert "imx: mmc_env: update runtime SD/MMC boot env device"

This reverts commit 34f2feb92db6146831bafa696b7b46785c9f6b10.

Signed-off-by: Stefano Babic <sbabic@denx.de>
diff --git a/arch/arm/mach-imx/mmc_env.c b/arch/arm/mach-imx/mmc_env.c
index addb50f..9c822f7 100644
--- a/arch/arm/mach-imx/mmc_env.c
+++ b/arch/arm/mach-imx/mmc_env.c
@@ -11,9 +11,6 @@
 
 __weak int board_mmc_get_env_dev(int devno)
 {
-	if (CONFIG_IS_ENABLED(DM_MMC))
-		return devno;
-
 	return CONFIG_SYS_MMC_ENV_DEV;
 }