MIPS: SGI-IP27: Remove not used includes and comment in ip27-timer.c

After commit 0ce5ebd2

 ("mfd: ioc3: Add driver for SGI IOC3 chip"),
the related includes and comment about ioc3 are not used any more in
ip27-timer.c, remove them.

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>