Fix namespace indentation and missing blank lines before 'public:' in *MCAsmInfo...

Fix namespace indentation and missing blank lines before 'public:' in *MCAsmInfo.h. NFC.

This is to reduce noise in a following commit.

Also fixes a couple missing spaces before the reference operator.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@247679 91177308-0d34-0410-b5e6-96231b3b80d8