regset: Add explicit core note name in struct user_regset

regset: Add explicit core note name in struct user_regset

There is currently hard-coded logic spread around the tree for
determining the note name for regset notes emitted in coredumps.

Now that the names are declared explicitly in <uapi/elf.h>, this can be
simplified.

In preparation for getting rid of the special-case logic, add an
explicit core_note_name field in struct user_regset for specifying the
note name explicitly.  To help avoid mistakes, a convenience macro
USER_REGSET_NOTE_TYPE() is provided to set .core_note_type and
.core_note_name based on the note type.

When dumping core, use the new field to set the note name, if the
regset specifies it.

Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Kees Cook <kees@kernel.org>
Cc: Akihiko Odaki <akihiko.odaki@daynix.com>
Acked-by: Alexander Gordeev <agordeev@linux.ibm.com> # s390
Reviewed-by: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>
Link: https://lore.kernel.org/r/20250701135616.29630-3-Dave.Martin@arm.com
Signed-off-by: Kees Cook <kees@kernel.org>