gas: x86: ginsn: handle previously missed indirect call and jmp ops

Some flavors of indirect call and jmp instructions were not being
handled earlier, leading to a GAS error (#1):
  (#1) "Error: SCFI: unhandled op 0xff may cause incorrect CFI"

Not handling jmp/call (direct or indirect) ops is an error (as shown
above) because SCFI needs an accurate CFG to synthesize CFI correctly.
Recall that the presence of indirect jmp/call, however, does make the
CFG ineligible for SCFI. In other words, generating the ginsns for them
now, will eventually cause SCFI to bail out later with an error (#2)
anyway:
  (#2) "Error: untraceable control flow for func 'XXX'"

The first error (#1) gives the impression of missing functionality in
GAS.  So, it seems cleaner to synthesize a GINSN_TYPE_JUMP /
GINSN_TYPE_CALL now in the backend, and let SCFI machinery complain with
the error as expected.

The handling for these indirect jmp/call instructions is similar, so
reuse the code by carving out a function for the same.

Adjust the testcase to include the now handled jmp/call instructions as
well.

gas/
	* config/tc-i386-ginsn.c (x86_ginsn_indirect_branch): New
	function.
	(x86_ginsn_new): Refactor out functionality to above.

gas/testsuite/
	* gas/scfi/x86_64/ginsn-cofi-1.l: Adjust the output.
	* gas/scfi/x86_64/ginsn-cofi-1.s: Add further varieties of
	jmp/call opcodes.