Reformatting the style used within the massive attribute semantic handling...

Reformatting the style used within the massive attribute semantic handling switch statement, so now there is only one style used in this block of code, instead of three or more styles.

No functional change intended.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@203120 91177308-0d34-0410-b5e6-96231b3b80d8