ARM: 6786/1: enable CONFIG_KTIME_SCALAR

Use straight 64-bit values as 64-bit operations are fairly efficient on ARM.
Comparing the asm output with and without KTIME_SCALAR, using 64-bit math
generates clearly better code.

Comparing kernel/hrtimer.c .text size, it goes from 0x1414 to 0x119c with
this change.
Signed-off-by: NRob Herring <rob.herring@calxeda.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

arch/arm/Kconfig

@@ -63,6 +63,10 @@ config GENERIC_CLOCKEVENTS_BROADCAST
 	depends on GENERIC_CLOCKEVENTS
 	default y if SMP
 
+config KTIME_SCALAR
+	bool
+	default y
+
 config HAVE_TCM
 	bool
 	select GENERIC_ALLOCATOR