configs: am6*_evm_a53_defconfig: Enable config to support mmc rescan

Enable MMC_SPEED_MODE_SET config option in defconfig to enable
mmc rescan for various Sitara devices.

Signed-off-by: Judith Mendez <jm@ti.com>
diff --git a/configs/am64x_evm_a53_defconfig b/configs/am64x_evm_a53_defconfig
index b7057be..179c42a 100644
--- a/configs/am64x_evm_a53_defconfig
+++ b/configs/am64x_evm_a53_defconfig
@@ -72,6 +72,7 @@
 CONFIG_CMD_TIME=y
 CONFIG_CMD_PMIC=y
 CONFIG_CMD_REGULATOR=y
+CONFIG_MMC_SPEED_MODE_SET=y
 CONFIG_OF_CONTROL=y
 CONFIG_SPL_OF_CONTROL=y
 CONFIG_OF_LIST="ti/k3-am642-evm ti/k3-am642-sk"