[RTC] remove references to asm/mach/time.h

asm/mach/time.h is the ARM header file for setting up kernel ticker
timekeeping (be that the old jiffy interrupt or the new clocksource.)
RTC drivers have no business using this header file, and in fact do
not require it.

Build tested on at91sam9rl, omap and s3c2410 configurations.

Acked-by: Alessandro Zummo <a.zummo@towertech.it>
Acked-by: Andrew Victor <linux@maxim.org.za>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>