Revert "MIPS: Lantiq: Fix cascaded IRQ setup"

This reverts commit 6280ac93 which is
commit 6c356eda upstream.

It shouldn't have been included in a stable release.

Reported-by: Amit Pundir <amit.pundir@linaro.org>
Cc: Felix Fietkau <nbd@nbd.name>
Cc: John Crispin <john@phrozen.org>
Cc: James Hogan <james.hogan@imgtec.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>