riscv/ptrace: Use USER_REGSET_NOTE_TYPE for REGSET_CFI

Fixes a warning while dumping core:

[54983.546369][    C7] WARNING: [!note_name] fs/binfmt_elf.c:1771 at elf_core_dump+0x910/0xf68, CPU#7: abort01/31982

Fixes: 2af7c9cf021c ("riscv/ptrace: expose riscv CFI status and state via ptrace and in core files")
Signed-off-by: Andreas Schwab <schwab@suse.de>
Link: https://patch.msgid.link/87y0hcxuh5.fsf@igel.home
Signed-off-by: Paul Walmsley <pjw@kernel.org>