Dynamically configure timers' base frequency for Armada 38x

Instead of using 'clock-frequency' device tree property for global/twd
mpcore timers of Armada 38x SoCs, set it in platform_late_init stage
with arm_tmr_change_frequency() function.

Reviewed by: cognet (mentor)
Approved by: cognet (mentor)
Obtained from: Semihalf
Differential Revision: https://reviews.freebsd.org/D11881

sys/arm/mv/mv_machdep.c

@@ -51,6 +51,7 @@ __FBSDID("$FreeBSD$");
 #include <vm/vm.h>
 #include <vm/pmap.h>
 
+#include <arm/arm/mpcore_timervar.h>
 #include <arm/arm/nexusvar.h>
 
 #include <machine/bus.h>
@@ -294,6 +295,9 @@ platform_late_init(void)
 #endif
 
 #if defined(SOC_MV_ARMADA38X)
+	/* Configure timers' base frequency */
+	arm_tmr_change_frequency(get_cpu_freq() / 2);
+
 	/*
 	 * Workaround for Marvell Armada38X family HW issue
 	 * between Cortex-A9 CPUs and on-chip devices that may