Add support for FPv4-SP to the clang driver

Added two new options for -mfpu when targetting ARM:
* fpv4-sp-d16
* fp4-sp-d16

The first is the same spelling as gcc.

The lack of a leading `v' is correct, this is consistent with ARM's
documentation and gcc's spelling of the option.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@201846 91177308-0d34-0410-b5e6-96231b3b80d8