armvirt: add kernel config change missing from 0d44f0cb

Signed-off-by: Felix Fietkau <[email protected]>

target/linux/armvirt/config-default

@@ -237,6 +237,7 @@ CONFIG_SYS_SUPPORTS_APM_EMULATION=y
 CONFIG_TICK_CPU_ACCOUNTING=y
 CONFIG_TREE_RCU=y
 CONFIG_UNCOMPRESS_INCLUDE="debug/uncompress.h"
+CONFIG_USB_SUPPORT=y
 CONFIG_USE_OF=y
 CONFIG_VECTORS_BASE=0xffff0000
 CONFIG_VFP=y