math/test-tgmath2: Fix fabs failure when no long double

math/test-tgmath2: Fix fabs failure when no long double

I have been testing with GCC trunk and GLIBC master while working on the
OpenRISC port.  This test has been failing with fabs not being called,
This is caused as my architecture is configure with no long double
meaning the two calls are the same:

  TEST (fabs (Vdouble1), double, fabs);
  TEST (fabs (Vldouble1), ldouble, fabs);

Instead of the tgmath calls resolving to fabs and fabsl both calls are
fabs.  Next, do to compiler optimiations the second call is eliminated.
Fix this by invoking the failing TEST with Vldouble2.

Note, I also updated the FAIL message to more clearly show where the
failure happened, so I see:

  FAIL: math/test-tgmath2
  original exit status 1
  wrong function called, fabs (ldouble) failure on line 174

Cc: Joseph Myers <joseph@codesourcery.com>