cpu,opcodes,gas: fix explicit arguments to eBPF ldabs instructions

cpu,opcodes,gas: fix explicit arguments to eBPF ldabs instructions

This patch fixes the eBPF CPU description in order to reflect the
right explicit arguments passed to the ldabs{b,h,w,dw} instructions,
updates the corresponding GAS tests, and updates the BPF section of
the GAS manual.

cpu/ChangeLog:

2019-07-15  Jose E. Marchesi  <jose.marchesi@oracle.com>

	* bpf.cpu (dlabs): New pmacro.
	(dlind): Likewise.

opcodes/ChangeLog:

2019-07-15  Jose E. Marchesi  <jose.marchesi@oracle.com>

	* bpf-desc.c: Regenerate.
	* bpf-opc.c: Likewise.
	* bpf-opc.h: Likewise.

gas/ChangeLog:

2019-07-15  Jose E. Marchesi  <jose.marchesi@oracle.com>

	* testsuite/gas/bpf/mem.s: ldabs instructions do not take a `src'
	register as an argument.
	* testsuite/gas/bpf/mem.d: Updated accordingly.
	* testsuite/gas/bpf/mem-be.d: Likewise.
	* doc/c-bpf.texi (BPF Opcodes): Update to reflect the correct
	explicit arguments to ldabs and ldind instructions.