ppc: Added macro to test for specific SVR revision

Various SoC errata are specific to a given revision of silicon. This
patch gives us a simple macro to use when doing such tests.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

include/asm-ppc/processor.h

@@ -992,6 +992,9 @@
 #endif
 #endif
 
+#define IS_SVR_REV(svr, maj, min) \
+	((SVR_MAJ(svr) == maj) && (SVR_MIN(svr) == min))
+
 /*
  * SVR_SOC_VER() Version Values
  */