sparc: Update cpu_init.c to use generic timer infrastructure

Introduce the CONFIG_SYS_TIMER_* macros in include/asm/config.h to make use
of the generic timer infrastructure in lib/time.c.

Created a timer_init() function to initialize the timer hardware and update
the #ifdef in board_init_f to allow this function to be called during the
start-up sequence.

Signed-off-by: Francois Retief <fgretief@spaceteq.co.za>
diff --git a/common/board_f.c b/common/board_f.c
index b035c90..2dd10b9 100644
--- a/common/board_f.c
+++ b/common/board_f.c
@@ -808,7 +808,8 @@
 	init_timebase,
 #endif
 #if defined(CONFIG_X86) || defined(CONFIG_ARM) || defined(CONFIG_MIPS) || \
-		defined(CONFIG_BLACKFIN) || defined(CONFIG_NDS32)
+		defined(CONFIG_BLACKFIN) || defined(CONFIG_NDS32) || \
+		defined(CONFIG_SPARC)
 	timer_init,		/* initialize timer */
 #endif
 #ifdef CONFIG_SYS_ALLOC_DPRAM