bpf: disasemble offsets of value 0 as "+0"

bpf: disasemble offsets of value 0 as "+0"

This tiny patch makes the BPF disassembler to emit, e.g.

  ldxdw %r1, [%r0+0]

instead of

  ldxdw %r1, [%r00]

when the offset is 0, to avoid confusion.

opcodes/

	* bpf-dis.c (print_insn_bpf): Print offsets with value 0 as "+0".

gas/

	* testsuite/gas/bpf/mem.s: Add tests with offset 0.
	* testsuite/gas/bpf/mem-pseudoc.s: Likewise.
	* testsuite/gas/bpf/mem.d: Update accordingly.
	* testsuite/gas/bpf/mem-be.d: Likewise.
	* testsuite/gas/bpf/mem-pseudoc.d: Likewise.
	* testsuite/gas/bpf/mem-be-pseudoc.d: Likewise.