powerpc: Don't do generic calibrate_delay()

Currently we are wasting time calling the generic calibrate_delay()
function. We don't need it since our implementation of __delay() is
based on the CPU timebase. So instead, we use our own small
implementation that initializes loops_per_jiffy to something sensible
to make the few users like spinlock debug be happy
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/Kconfig

@@ -93,10 +93,6 @@ config GENERIC_HWEIGHT
 	bool
 	default y
 
-config GENERIC_CALIBRATE_DELAY
-	bool
-	default y
-
 config GENERIC_FIND_NEXT_BIT
 	bool
 	default y

arch/powerpc/kernel/time.c

@@ -52,6 +52,7 @@
 #include <linux/jiffies.h>
 #include <linux/posix-timers.h>
 #include <linux/irq.h>
+#include <linux/delay.h>
 
 #include <asm/io.h>
 #include <asm/processor.h>
@@ -1143,6 +1144,15 @@ void div128_by_32(u64 dividend_high, u64 dividend_low,
 
 }
 
+/* We don't need to calibrate delay, we use the CPU timebase for that */
+void calibrate_delay(void)
+{
+	/* Some generic code (such as spinlock debug) use loops_per_jiffy
+	 * as the number of __delay(1) in a jiffy, so make it so
+	 */
+	loops_per_jiffy = tb_ticks_per_jiffy;
+}
+
 static int __init rtc_init(void)
 {
 	struct platform_device *pdev;