static_call: Avoid building empty .static_call_sites

Without CONFIG_HAVE_STATIC_CALL_INLINE there's no point in creating
the .static_call_sites section and it's related symbols.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20220308154317.223798256@infradead.org