fixes #1774
clang is not recognizing some pre-UAL VFP mnemonics like fnmacs, fnmacd, fnmuls and fnmuld. Replaced them with equivalent UAL mnemonics which are vmls.f32, vmls.f64, vnmul.f32 and vnmul.f64 respectively.
Signed-off-by: Timothy Gu <timothygu99@gmail.com>