SPARC: Migrate from 'regset_from_core_section' to 'iterate_over_regset_sections'

SPARC: Migrate from 'regset_from_core_section' to 'iterate_over_regset_sections'

For SPARC targets, no longer define the gdbarch method
'regset_from_core_section', but the iterator method instead.

gdb/ChangeLog:

	* sparc-tdep.c (sparc_regset_from_core_section): Remove.
	(sparc_iterate_over_regset_sections): New.
	(sparc32_gdbarch_init): Adjust gdbarch initialization.
	* configure.tgt (gdb_target_obs): Add fbsd-tdep.o for SPARC FreeBSD
	targets.
	* sparc64fbsd-tdep.c (fbsd-tdep.h): Include.
	(sparc64fbsd_init_abi): Call fbsd_init_abi.
	* sparc64fbsd-nat.c (_initialize_sparc64fbsd_nat): Do not set
	target method 'make_corefile_notes'.