bpf: fix generation of neg and neg32 BPF instructions

bpf: fix generation of neg and neg32 BPF instructions

This patch fixes GCC to generate correct neg and neg32 instructions,
which do not take a source register operand.  A couple of new tests
are added.

Tested in bpf-unknown-none.

gcc/ChangeLog

2023-07-26  Jose E. Marchesi  <jose.marchesi@oracle.com>

	* config/bpf/bpf.md: Fix neg{SI,DI}2 insn.

gcc/testsuite/ChangeLog

2023-07-26  Jose E. Marchesi  <jose.marchesi@oracle.com>

	* gcc.target/bpf/neg-1.c: New test.
	* gcc.target/bpf/neg-pseudoc-1.c: Likewise.