Add 3 new PAC-related ARM note types

Add 3 new PAC-related ARM note types

The following patch synchronizes includes/objdump/readelf with the Linux
Kernel in terms of ARM regset notes.

We're currently missing 3 of them:

NT_ARM_PACA_KEYS
NT_ARM_PACG_KEYS
NT_ARM_PAC_ENABLED_KEYS

We don't need GDB to bother with this at the moment, so this doesn't update
bfd/elf.c. If needed, we can do it in the future.

binutils/

	* readelf.c (get_note_type): Handle new ARM PAC notes.

include/elf/

	* common.h (NT_ARM_PACA_KEYS, NT_ARM_PACG_KEYS)
	(NT_ARM_PAC_ENABLED_KEYS): New constants.