imx: mx6sllevk: add usb support

Add usb support for mx6sllevk board.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Cc: Stefano Babic <sbabic@denx.de>
diff --git a/configs/mx6sllevk_defconfig b/configs/mx6sllevk_defconfig
index 8ae049e..267cdc6 100644
--- a/configs/mx6sllevk_defconfig
+++ b/configs/mx6sllevk_defconfig
@@ -10,6 +10,7 @@
 CONFIG_CMD_MEMTEST=y
 CONFIG_CMD_MMC=y
 CONFIG_CMD_I2C=y
+CONFIG_CMD_USB=y
 CONFIG_CMD_GPIO=y
 CONFIG_CMD_DHCP=y
 CONFIG_CMD_PING=y
@@ -34,3 +35,7 @@
 CONFIG_DM_REGULATOR_PFUZE100=y
 CONFIG_DM_REGULATOR_FIXED=y
 CONFIG_DM_REGULATOR_GPIO=y
+CONFIG_USB=y
+CONFIG_DM_USB=y
+CONFIG_USB_EHCI_HCD=y
+CONFIG_USB_STORAGE=y