m68hc11/12 and xgate config.sub weirdness

Oddly, config.sub converts a duple ending in -elf for these target to
-unknown-none, which means they aren't seen as elf targets by
binutils.  So, counter that.  This exposes a number of testsuite
issues (ones you would have seen if configuring with a full triple,
say m68hc11-unknown-elf).

binutils/
	* testsuite/lib/binutils-common.exp (is_elf_format): Return true
	for m68hc11/12 and xgate triples.
gas/
	* testsuite/gas/cfi/cfi.exp: Exclude m68hc11/12 from m68k test.
ld/
	* testsuite/lib/ld-lib.exp (check_shared_lib_support): Exclude xgate.
	* testsuite/ld-elf/endsym.d: xfail m68hc11/12 and xgate.
	* testsuite/ld-elf/pr14156a.d: Likewise.
	* testsuite/ld-elf/pr14926.d: Don't run for m68hc11/12 and xgate.
	* testsuite/ld-elf/sec64k.exp: Likewise.