ARM: pxa: convert sched_clock() to use new infrastructure

Convert pxa to use the new sched_clock() infrastructure for extending
32bit counters to full 64-bit nanoseconds.

Tested-by: Eric Miao <eric.y.miao@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 0208e1e..23035d6 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -593,6 +593,7 @@
 	select COMMON_CLKDEV
 	select ARCH_REQUIRE_GPIOLIB
 	select GENERIC_CLOCKEVENTS
+	select HAVE_SCHED_CLOCK
 	select TICK_ONESHOT
 	select PLAT_PXA
 	select SPARSE_IRQ