x86-64: Add vector cos/cosf to libmvec microbenchmark

Add vector cos/cosf and input files to libmvec microbenchmark.

libmvec-cos-inputs:
  90% Normal random distribution
  range: (-DBL_MAX, DBL_MAX)
  mean: 0.0
  sigma: 5.0
  10% uniform random distribution in range (-1000.0, 1000.0)

libmvec-cosf-inputs:
  90% Normal random distribution
  range: (-FLT_MAX, FLT_MAX)
  mean: 0.0f
  sigma: 5.0f
  10% uniform random distribution in range (-1000.0f, 1000.0f)

Reviewed-by: H.J. Lu <hjl.tools@gmail.com>

sysdeps/x86_64/fpu/Makeconfig

@@ -31,6 +31,7 @@ libmvec-funcs = \
 
 # Define libmvec function for benchtests directory.
 libmvec-bench-funcs = \
+  cos \
 
 bench-libmvec-double = \
   $(addprefix double-vlen1-, $(libmvec-bench-funcs)) \