Function ffs_do_functionfs_bind() calls functionfs_bind() which allocates
usb request and increments refcounts. These things needs to be cleaned
up by if further steps of initialization fail by calling functionfs_unbind().
Signed-off-by: Robert Baldyga <r.baldyga@samsung.com> Acked-by: Michal Nazarewicz <mina86@mina86.com> Signed-off-by: Felipe Balbi <balbi@ti.com>