HPPA: Migrate from 'regset_from_core_section' to 'iterate_over_regset_sections'

HPPA: Migrate from 'regset_from_core_section' to 'iterate_over_regset_sections'

For HP PA-RISC targets, no longer define the gdbarch method
'regset_from_core_section', but the iterator method instead.

gdb/ChangeLog:

	* hppa-hpux-tdep.c (hppa_hpux_regset_from_core_section): Remove.
	(hppa_hpux_iterate_over_regset_sections): New.
	(hppa_hpux_init_abi): Adjust gdbarch initialization.
	* hppa-linux-tdep.c (hppa_linux_regset_from_core_section): Remove.
	(hppa_linux_iterate_over_regset_sections): New.
	(hppa_linux_init_abi): Adjust.
	* hppanbsd-tdep.c (hppaobsd_regset_from_core_section): Remove.
	(hppanbsd_iterate_over_regset_sections): New.
	(hppanbsd_init_abi): Adjust.
	* hppaobsd-tdep.c (hppaobsd_regset_from_core_section): Remove.
	(hppaobsd_iterate_over_regset_sections): New.
	(hppaobsd_init_abi): Adjust.