Define Neon intrinsics as "static inline" to avoid warning. rdar://13108414

We had been defining Neon intrinsics as "static" with always_inline attributes.
If you use them from an extern inline function, you get a warning, e.g.:

static function 'vadd_u8' is used in an inline function with external linkage

This change simply adds the inline keyword to avoid that warning.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@179406 91177308-0d34-0410-b5e6-96231b3b80d8