MUSB: Fix index register corruption seen with g_ether and Windows host

If Indexed Mode register accesses are enabled, the ep0_rxstate()
function calls musb_g_ep0_giveback() before writing to the CSR
register. When control returns to this ep0_rxstate, the index
register contents are over-written. This causes the CSR register
write to fail.

Fixed by writing the correct value into the index register before
writing to the CSR.

This was observed only in ep0_rxstate() with g_ether loaded and
the device connected to a MS Windows host PC. Anticipatively fixed
ep0_txstate() as well.

Signed-off-by: Anand Gadiyar <gadiyar@ti.com>
Acked-by: Felipe Balbi <felipe.balbi@nokia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/musb/musb_gadget_ep0.c

@@ -476,6 +476,7 @@ static void ep0_rxstate(struct musb *musb)
 			return;
 		musb->ackpend = 0;
 	}
+	musb_ep_select(musb->mregs, 0);
 	musb_writew(regs, MUSB_CSR0, tmp);
 }
 
@@ -528,6 +529,7 @@ static void ep0_txstate(struct musb *musb)
 	}
 
 	/* send it out, triggering a "txpktrdy cleared" irq */
+	musb_ep_select(musb->mregs, 0);
 	musb_writew(regs, MUSB_CSR0, csr);
 }