xtensa: move xtensa_make_property_section from bfd to gas

xtensa: move xtensa_make_property_section from bfd to gas

This function is only used by gas, so move it there.  Necessary for
gas to keep track of group sections as they are created.

	PR 25333
bfd/
	* elf32-xtensa.c (xtensa_make_property_section): Delete.
	(xtensa_property_section_name): Make public.
include/
	* elf/xtensa.h (xtensa_make_property_section): Delete.
	(xtensa_property_section_name): Declare
gas/
	* config/tc-xtensa.c (xtensa_make_property_section): New,
	moved from elf32-xtensa.c.