[ARM] support for Cortex-R4/R4F

Currently, llvm (backend) doesn't know cortex-r4, even though it is the
default target for armv7r. Using "--target=armv7r-arm-none-eabi" provokes
'cortex-r4' is not a recognized processor for this target' by llvm.
This patch adds support for cortex-r4 and, very closely related, r4f.

llvm-svn: 234486
diff --git a/llvm/lib/Target/ARM/ARMSubtarget.h b/llvm/lib/Target/ARM/ARMSubtarget.h
index b8e8242..0b8b780 100644
--- a/llvm/lib/Target/ARM/ARMSubtarget.h
+++ b/llvm/lib/Target/ARM/ARMSubtarget.h
@@ -43,7 +43,7 @@
 protected:
   enum ARMProcFamilyEnum {
     Others, CortexA5, CortexA7, CortexA8, CortexA9, CortexA12, CortexA15,
-    CortexA17, CortexR5, Swift, CortexA53, CortexA57, Krait, 
+    CortexA17, CortexR4, CortexR4F, CortexR5, Swift, CortexA53, CortexA57, Krait,
   };
   enum ARMProcClassEnum {
     None, AClass, RClass, MClass