bpf: Update atomic instruction pseudo-C syntax

bpf: Update atomic instruction pseudo-C syntax

This patch updates the pseudo-C dialect templates for the BPF v3 atomic
instructions.  The templates match the strings emitted by clang -S for
these instructions.

The tests and documentation are updated accordingly.

gas/
	* doc/c-bpf.texi (BPF Instructions): Update entries for atomic
	and 32-bit atomic instructions.
	* testsuite/gas/bpf/atomic.s: Test AAND, AAND32, AOR, AOR32,
	AXOR, AXOR32, AFADD, AFADD32, AFAND, AFAND32, AFOR, AFOR32,
	AFXOR and AFXOR32 instructions.
	* testsuite/gas/bpf/atomic.d: Likewise.
	* testsuite/gas/bpf/atomic-be.d: Likewise.
	* testsuite/gas/bpf/atomic-pseudoc.s: Likewise.
	* testsuite/gas/bpf/atomic-pseudoc.d: Likewise.
	* testsuite/gas/bpf/atomic-be-pseudoc.d: Likewise.
	* testsuite/gas/bpf/atomic-v1.s: New test.
	* testsuite/gas/bpf/atomic-v1.d: Likewise.
	* testuiste/gas/bpf/atomic-v1-be.d: Likewise.
	* testuiste/gas/bpf/bpf.exp: Run new tests.

opcodes/
	* bpf-opc.c (bpf_opcodes): Update pseudo-C dialect templates for:
	BPF_INSN_AADD, BPF_INSN_AOR, BPF_INSN_AAND, BPF_INSN_AXOR,
	BPF_INSN_AFADD, BPF_INSN_AFOR, BPF_INSN_AFAND, BPF_INSN_AFXOR,
	BPF_INSN_AADD32, BPF_INSN_AOR32, BPF_INSN_AAND32,
	BPF_INSN_AXOR32, BPF_INSN_AFADD32, BPF_INSN_AFOR32,
	BPF_INSN_AFAND32, and BPF_INSN_AFXOR32 instructions.