[ARM] 3443/1: [S3C2410] Improve IRQ entry code

Patch from Ben Dooks

Remove the old debug from the IRQ entry code,
update the comments on the handling of the
IRQ registers.

The message "bad interrupt offset" is removed
as it is only helpful for debugging, and can
cause printk() flooding when under load.

Make the code to deal with GPIO interrupts
faster, and use the same path to deal with
unexplained results from the IRQ registers.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>