usb: musb: gadget: restart request on clearing endpoint halt

Commit 46034dca (USB: musb_gadget_ep0: stop
abusing musb_gadget_set_halt()) forgot to restart a queued request after
clearing the endpoint halt feature. This results in a couple of USB resets
while enumerating the file-backed storage gadget due to CSW packet not being
sent for the MODE SENSE(10) command.

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Cc: stable@kernel.org
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>