goldfish: Sanitize the broken interrupt handler

This interrupt handler is broken in several ways:

  - It loops forever when the op code is not decodeable

  - It never returns IRQ_HANDLED because the only way to exit the loop
    returns IRQ_NONE unconditionally.

The whole concept of this is broken. Creating devices in an interrupt
handler is beyond any point of sanity.

Make it at least behave halfways sane so accidental users do not have to
deal with a hard to debug lockup.

Fixes: e809c22b ("goldfish: add the goldfish virtual bus")
Reported-by: Gabriel C <nix.or.die@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>