posix-timers: Convert clock_getres() to clockid_to_kclock()

Use the new kclock decoding. Fixup the fallout in mmtimer.c

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <johnstul@us.ibm.com>
Tested-by: Richard Cochran <richard.cochran@omicron.at>
LKML-Reference: <20110201134418.709802797@linutronix.de>