nios2: convert altera timer to driver model

Convert altera timer to driver model.

Signed-off-by: Thomas Chou <thomas@wytron.com.tw>
Acked-by: Chin Liang See <clsee@altera.com>
diff --git a/drivers/timer/Makefile b/drivers/timer/Makefile
index afb0009..ae66c07 100644
--- a/drivers/timer/Makefile
+++ b/drivers/timer/Makefile
@@ -5,3 +5,4 @@
 #
 
 obj-$(CONFIG_TIMER)		+= timer-uclass.o
+obj-$(CONFIG_ALTERA_TIMER)	+= altera_timer.o