Revert part of commit 8e885fece150

After commit 5e83077d552e we no longer choose a "plugin" target in
objcopy so ibfd->target_defaults can again be used to test whether the
user supplied a target.

	PR 33230
	* objcopy.c (copy_file): Revert change adding a target_defaulted
	variable and passing down to..
	(copy_archive, copy_object): ..here.  Remove target_defaulted
	parameter.  Use ibfd->target_defaulted.