Revert "USB: pxa2xx_udc: fix hardcoded irq number"

This reverts commit d2487cb4

.

Russell King points out that it's obviously bogus, and I have to agree.
Not only does "irq" not even exist in that scope, but we obviously need
to free the irq that we actually requested, and that's IRQ_USB.

Reported-by: Russell King <rmk@arm.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Greg KH <greg@kroah.com>
Cc: David Brownell <david-b@pacbell.net>,
Cc: Milan Svoboda <msvoboda@ra.rockwell.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>