recovery: Fix adb with linux 3.10

In kernel 3.10, f_adb has been removed and adbd can use functionfs
instead. Mount functionfs on boot for adbd. On older kernels, mount
will fail silently and adbd will revert to f_adb.

Change-Id: I5db57aaf35b35859ea88c7d0e0661d8c553e5811

etc/init.rc

@@ -21,9 +21,15 @@ on init
     chown root shell /tmp
     chmod 0775 /tmp
 
+on fs
+    mkdir /dev/usb-ffs 0770 shell shell
+    mkdir /dev/usb-ffs/adb 0770 shell shell
+    mount functionfs adb /dev/usb-ffs/adb uid=2000,gid=2000
+
     write /sys/class/android_usb/android0/enable 0
     write /sys/class/android_usb/android0/idVendor 18D1
     write /sys/class/android_usb/android0/idProduct D002
+    write /sys/class/android_usb/android0/f_ffs/aliases adb
     write /sys/class/android_usb/android0/functions adb
     write /sys/class/android_usb/android0/iManufacturer ${ro.product.manufacturer}
     write /sys/class/android_usb/android0/iProduct ${ro.product.model}
@@ -92,4 +98,4 @@ on property:ro.debuggable=1
 on property:service.adb.root=1
     write /sys/class/android_usb/android0/enable 0
     restart adbd
-    write /sys/class/android_usb/android0/enable 1
+    write /sys/class/android_usb/android0/enable 1