musb_gadget: fix unhandled endpoint 0 IRQs

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.

The driver also prematurely leaves the status phase on
receiving the SetupEnd interrupt.

As there were still unhandled endpoint 0 interrupts happening
from time to time after fixing these issues, there turned to
be yet another culprit: two distinct gadget states collapsed
into one.

The (missing) state that comes after STATUS IN/OUT states was
typically indiscernible from them since the corresponding
interrupts tend to happen within too little period of time
(due to only a zero-length status packet in between) and so
they got coalesced; yet this state is not the same as the next
one which is associated with the reception of a SETUP packet.

Adding this extra state seems to have fixed the rest of the
unhandled interrupts that generic_interrupt() and
davinci_interrupt() hid by faking their result and only
emitting a debug message -- so, stop doing that.

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>