[ARM] rtc-sa1100: don't assume CLOCK_TICK_RATE to be a constant

As Nicolas and Russell pointed out, CLOCK_TICK_RATE is no more
a constant on PXA when multiple processors and platforms are
selected, change TIMER_FREQ in rtc-sa1100.c into a variable.

Since the code to decide the clock tick rate is re-used from
timer.c, introduce a common get_clock_tick_rate() for this.

Signed-off-by: Eric Miao <eric.miao@marvell.com>
Acked-by: Nicolas Pitre <nico@marvell.com>
diff --git a/arch/arm/mach-pxa/generic.c b/arch/arm/mach-pxa/generic.c
index 85ed0b3..0ccc91c 100644
--- a/arch/arm/mach-pxa/generic.c
+++ b/arch/arm/mach-pxa/generic.c
@@ -24,6 +24,7 @@
 #include <asm/system.h>
 #include <asm/pgtable.h>
 #include <asm/mach/map.h>
+#include <asm/mach-types.h>
 
 #include <mach/pxa-regs.h>
 #include <mach/reset.h>
@@ -39,6 +40,21 @@
 		pxa3xx_clear_reset_status(mask);
 }
 
+unsigned long get_clock_tick_rate(void)
+{
+	unsigned long clock_tick_rate;
+
+	if (cpu_is_pxa25x())
+		clock_tick_rate = 3686400;
+	else if (machine_is_mainstone())
+		clock_tick_rate = 3249600;
+	else
+		clock_tick_rate = 3250000;
+
+	return clock_tick_rate;
+}
+EXPORT_SYMBOL(get_clock_tick_rate);
+
 /*
  * Get the clock frequency as reflected by CCCR and the turbo flag.
  * We assume these values have been applied via a fcs.