x86: testsuite: scfi: adjust COFI testcase

x86: testsuite: scfi: adjust COFI testcase

The testcase for change of flow instructions in its current shape is not
doing much: it checks that SCFI issues an appropriate warning.  The same
warning is covered by another testcase (scfi-unsupported-cfg-1); It is
better to test the ginsn translation instead, for these 'change of flow
instructions'.

gas/testsuite/
	* gas/scfi/x86_64/scfi-cofi-1.s: Moved to...
	* gas/scfi/x86_64/ginsn-cofi-1.s: ...here.
	* gas/scfi/x86_64/scfi-x86-64.exp: Adjust tests.
	* gas/scfi/x86_64/scfi-cofi-1.d: Removed.
	* gas/scfi/x86_64/scfi-cofi-1.l: Removed.
	* gas/scfi/x86_64/ginsn-cofi-1.l: New test.