timekeeping: Fix up read_persistent_clock() breakage on sh

The recent commit "timekeeping: Increase granularity of
read_persistent_clock()" introduced read_persistent_clock()
rework which inadvertently broke the sh conversion:

	arch/sh/kernel/time.c:45: error: passing argument 1 of 'rtc_sh_get_time' from incompatible pointer type
	distcc[13470] ERROR: compile arch/sh/kernel/time.c on sprygo/32 failed
	make[2]: *** [arch/sh/kernel/time.o] Error 1

This trivial fix gets it working again.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
LKML-Reference: <20090824223239.GB20832@linux-sh.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>