powerpc: Merge time.c and asm/time.h.

We now use the merged time.c for both 32-bit and 64-bit compilation
with ARCH=powerpc, and for ARCH=ppc64, but not for ARCH=ppc32.
This removes setup_default_decr (folds its function into time_init)
and moves wakeup_decrementer into time.c.  This also makes an
asm-powerpc/rtc.h.

Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/ppc/kernel/time.c b/arch/ppc/kernel/time.c
index 22d7fd1..76f44ce 100644
--- a/arch/ppc/kernel/time.c
+++ b/arch/ppc/kernel/time.c
@@ -121,6 +121,15 @@
 EXPORT_SYMBOL(profile_pc);
 #endif
 
+void wakeup_decrementer(void)
+{
+	set_dec(tb_ticks_per_jiffy);
+	/* No currently-supported powerbook has a 601,
+	 * so use get_tbl, not native
+	 */
+	last_jiffy_stamp(0) = tb_last_stamp = get_tbl();
+}
+
 /*
  * timer_interrupt - gets called when the decrementer overflows,
  * with interrupts disabled.