Added __builtin_riscv_cv_simd_neg_[h,b]

[MaryBennett]

Issue #54 CORE-V: SIMD __builtin_riscv_cv_simd_neg_h and __builtin_riscv_cv_simd_neg_b needs implementing

Files Changed:

• config/riscv/corev.def: Added new builtins.
• config/riscv/corev.md: Likewise.
• testsuite/gcc.target/riscv/cv-simd-neg-b-compile-1.c: Created.
• testsuite/gcc.target/riscv/cv-simd-neg-h-compile-1.c: Likewise.

[MaryBennett]

Regression test for target_board= riscv-sim

                === gcc Summary ===

                              Previous		This commit
# of expected passes            196019		196047
# of unexpected failures        19517		19517
# of unexpected successes       2		2
# of expected failures          839		839
# of unresolved testcases       5		5
# of unsupported tests          4023		4023

[jeremybennett]

Reviewed. Looks good to merge.