bpf: use elfos.h

bpf: use elfos.h

BPF is an ELF-based target, so it definitely benefits from using
elfos.h.  This patch makes the target to use it, and removes
superfluous definitions from bpf.h which are better defined in
elfos.h.

Note that BPF, despite being an ELF target, doesn't use DWARF.  At
some point it will generate DWARF when generating xBPF (-mxbpf) and
BTF when generating plain eBPF, but for the time being it just
generates stabs.

2020-09-02  Jose E. Marchesi  <jemarch@gnu.org>

	gcc/
	* config.gcc: Use elfos.h in bpf-*-* targets.
	* config/bpf/bpf.h (MAX_OFILE_ALIGNMENT): Remove definition.
	(COMMON_ASM_OP): Likewise.
	(INIT_SECTION_ASM_OP): Likewise.
	(FINI_SECTION_ASM_OP): Likewise.
	(ASM_OUTPUT_SKIP): Likewise.
	(ASM_OUTPUT_ALIGNED_COMMON): Likewise.
	(ASM_OUTPUT_ALIGNED_LOCAL): Likewise.