testsuite: Adjust scalar-test-neg-8.c with lp64 [PR108730]

testsuite: Adjust scalar-test-neg-8.c with lp64 [PR108730]

The built-in function scalar_test_neg_qp is under stanza
ieee128-hw, that is TARGET_FLOAT128_HW.  Since we don't
have float128 hardware support on 32-bit as follows:

if (TARGET_FLOAT128_HW && !TARGET_64BIT)
  {
    if ((rs6000_isa_flags_explicit & OPTION_MASK_FLOAT128_HW) != 0)
      error ("%qs requires %qs", "%<-mfloat128-hardware%>", "-m64");
    rs6000_isa_flags &= ~OPTION_MASK_FLOAT128_HW;
  }

So adjust the case with lp64 effective target accordingly.

	PR testsuite/108730

gcc/testsuite/ChangeLog:

	* gcc.target/powerpc/bfp/scalar-test-neg-8.c: Adjust with lp64
	effective target requirement.