USB: musb: gadget_ep0: avoid SetupEnd interrupt

Gadget stalling a zero-length SETUP request results in this error message:

SetupEnd came in a wrong ep0stage idle

In order to avoid it, always set the CSR0.DataEnd bit after detecting a zero-
length request.  Add the missing '\n' to the error message itself as well...

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