USB: musb_core: make disconnect and suspend interrupts work again

Commit 1c25fda4

 (usb: musb: handle irqs in the
order dictated by programming guide) forgot to get rid of the old 'STAGE0_MASK'
filter for calling musb_stage0_irq(), so now disconnect and suspend interrupts
are effectively ignored...

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