driver: timer: Add the Atmel PIT timer driver

Add the new Atmel PIT timer driver, which supports the driver model
and device tree.

Signed-off-by: Wenyou Yang <wenyou.yang@microchip.com>
diff --git a/arch/arm/mach-at91/armv7/Makefile b/arch/arm/mach-at91/armv7/Makefile
index 9538bc1..1ede4cb 100644
--- a/arch/arm/mach-at91/armv7/Makefile
+++ b/arch/arm/mach-at91/armv7/Makefile
@@ -14,4 +14,6 @@
 obj-y += clock.o
 obj-y += cpu.o
 obj-y += reset.o
+ifeq ($(CONFIG_ATMEL_PIT_TIMER),)
 obj-y += timer.o
+endif