USB: musb_gadget_ep0: fix unhandled endpoint 0 IRQs, again

Commit a5073b52 (musb_gadget: fix
unhandled endpoint 0 IRQs) somehow missed its key change:

"The gadget EP0 code routinely ignores an interrupt at end of
the data phase because of musb_g_ep0_giveback() resetting the
state machine to "idle, waiting for SETUP" phase prematurely."

So, the majority of the cases of unhandled IRQs is still unfixed...

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