powerpc: Convert feature_lock to raw_spinlock

feature_lock needs to be a real spinlock in RT. Convert it to
raw_spinlock.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/include/asm/pmac_feature.h b/arch/powerpc/include/asm/pmac_feature.h
index 877c35a..00eedc5 100644
--- a/arch/powerpc/include/asm/pmac_feature.h
+++ b/arch/powerpc/include/asm/pmac_feature.h
@@ -378,7 +378,7 @@
  * Those are exported by pmac feature for internal use by arch code
  * only like the platform function callbacks, do not use directly in drivers
  */
-extern spinlock_t feature_lock;
+extern raw_spinlock_t feature_lock;
 extern struct device_node *uninorth_node;
 extern u32 __iomem *uninorth_base;