[POWERPC] 40x decrementer fixes

Allow generic_calibrate_decr to work for 40x platforms.  Given that the hardware
behavior is identical, this also changes the set_dec function to reload the PIT
on 40x to match the behavior 44x currently has.

Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>
diff --git a/include/asm-powerpc/time.h b/include/asm-powerpc/time.h
index d7f5ddf..fdc271e 100644
--- a/include/asm-powerpc/time.h
+++ b/include/asm-powerpc/time.h
@@ -174,7 +174,7 @@
 static inline void set_dec(int val)
 {
 #if defined(CONFIG_40x)
-	return;		/* Have to let it auto-reload */
+	mtspr(SPRN_PIT, val);
 #elif defined(CONFIG_8xx_CPU6)
 	set_dec_cpu6(val);
 #else