[FunctionAttrs] Rename functionattrs -> function-attrs

To match NewPM pass name, and also for readability.
Also rename rpo-functionattrs -> rpo-function-attrs while we're here.

Reviewed By: arsenm

Differential Revision: https://reviews.llvm.org/D84694
diff --git a/llvm/test/Transforms/FunctionAttrs/nounwind.ll b/llvm/test/Transforms/FunctionAttrs/nounwind.ll
index 6d5e3a2..57518f4 100644
--- a/llvm/test/Transforms/FunctionAttrs/nounwind.ll
+++ b/llvm/test/Transforms/FunctionAttrs/nounwind.ll
@@ -1,4 +1,4 @@
-; RUN: opt < %s -functionattrs -S | FileCheck %s
+; RUN: opt < %s -function-attrs -S | FileCheck %s
 
 ; TEST 1
 ; CHECK: Function Attrs: norecurse nounwind readnone