configs: am43xx_evm: Enable USB support

spl_dm_init is failing as usb to be probed with the following error:
"omap_dwc3@483c0000: ret=-2"
Enable usb to make spl boot on am43xx devices

Reported-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
diff --git a/configs/am43xx_evm_defconfig b/configs/am43xx_evm_defconfig
index 7367c69..5e3e01c 100644
--- a/configs/am43xx_evm_defconfig
+++ b/configs/am43xx_evm_defconfig
@@ -18,6 +18,7 @@
 CONFIG_SPL_NET_SUPPORT=y
 CONFIG_SPL_NET_VCI_STRING="AM43xx U-Boot SPL"
 CONFIG_SPL_OS_BOOT=y
+CONFIG_SPL_USB_HOST_SUPPORT=y
 CONFIG_SPL_USB_GADGET=y
 CONFIG_SPL_USB_ETHER=y
 CONFIG_CMD_SPL=y