au1550_spi: fix prototype of irq handler

Remove struct pt_regs *regs from prototype of au1550_spi_irq handler to avoid
warning in request_irq().  Also fix comment type leadin.

Signed-off-by: Jan Nikitenko <jan.nikitenko@gmail.com>
Signed-off-by: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>