ast2500: defconfig: Add USB Mass Storage

USB Mass Storage will be used for implementing Virtual Media.

This adds about 800 bytes to the kernel image:
Before:
-rw-r--r-- 2 anoo anoo  2582512 Jan 22 09:57 fitImage--4.19.16+git0+bbc22aa295-r0-witherspoon-20190122155444.bin
After:
-rw-r--r-- 2 anoo anoo  2583344 Jan 22 10:02 fitImage--4.19.16+git0+bbc22aa295-r0-witherspoon-20190122160056.bin

(From meta-aspeed rev: f7c9426e180f46dedd04ac0b671064ba792cff28)

Change-Id: If453830f4e55c2abbb8cd703f589b7caf24fafd6
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/meta-aspeed/recipes-kernel/linux/ast2500/defconfig b/meta-aspeed/recipes-kernel/linux/ast2500/defconfig
index 2869a64..7d34e15 100755
--- a/meta-aspeed/recipes-kernel/linux/ast2500/defconfig
+++ b/meta-aspeed/recipes-kernel/linux/ast2500/defconfig
@@ -193,6 +193,7 @@
 CONFIG_USB_ASPEED_VHUB=y
 CONFIG_USB_CONFIGFS=y
 CONFIG_USB_CONFIGFS_MASS_STORAGE=y
+CONFIG_USB_MASS_STORAGE=y
 CONFIG_NEW_LEDS=y
 CONFIG_LEDS_CLASS=y
 CONFIG_LEDS_CLASS_FLASH=y