USB: at91_udc: correct hanging while disconnecting usb cable

Correct hanging while disconnecting the USB device cable.  Prevent a race
between vbus and UDP interrupts.  This bug was tracked on at91sam9260ek
boards.

A usb resume interrupt was firing after the vbus interrupt : the IP was
then already stoped and not able to deal with it (no more clock).  A simple
interrupt disabling is ok as the "end of bus reset" irq is non maskable and
ok to resume the USB device IP.
Signed-off-by: Nicolas Ferre <nicolas.ferre@rfo.atmel.com>
Acked-by: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/gadget/at91_udc.c

@@ -887,6 +887,7 @@ static void pullup(struct at91_udc *udc, int is_on)
 
 	if (is_on) {
 		clk_on(udc);
+		at91_udp_write(udc, AT91_UDP_ICR, AT91_UDP_RXRSM);
 		at91_udp_write(udc, AT91_UDP_TXVC, 0);
 		if (cpu_is_at91rm9200())
 			at91_set_gpio_value(udc->board.pullup_pin, 1);
@@ -904,6 +905,7 @@ static void pullup(struct at91_udc *udc, int is_on)
 		}
 	} else {
 		stop_activity(udc);
+		at91_udp_write(udc, AT91_UDP_IDR, AT91_UDP_RXRSM);
 		at91_udp_write(udc, AT91_UDP_TXVC, AT91_UDP_TXVC_TXVDIS);
 		if (cpu_is_at91rm9200())
 			at91_set_gpio_value(udc->board.pullup_pin, 0);