langwell_gpio: modify EOI handling following change of kernel irq subsystem

Latest kernel has many changes in IRQ subsystem and its interfaces, like
adding "irq_eoi" for struct irq_chip, this patch is a follow up change
for that.

Also remove the unnecessary cast for a "void *".

Signed-off-by: Feng Tang <feng.tang@intel.com>
Cc: Alek Du <alek.du@intel.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>