elfnote: Change ELFNOTE() to use __UNIQUE_ID()

elfnote: Change ELFNOTE() to use __UNIQUE_ID()

In preparation for the objtool klp diff subcommand, replace the custom
unique symbol name generation in ELFNOTE() with __UNIQUE_ID().

This standardizes the naming format for all "unique" symbols, which will
allow objtool to properly correlate them.  Note this also removes the
"one ELF note per line" limitation.

Acked-by: Petr Mladek <pmladek@suse.com>
Tested-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>