x86/alternatives: Remove the 'addr == NULL means forced-flush' hack from smp_text_pok...

x86/alternatives: Remove the 'addr == NULL means forced-flush' hack from smp_text_poke_batch_finish()/smp_text_poke_batch_flush()/text_poke_addr_ordered()

There's this weird hack used by smp_text_poke_batch_finish() to indicate
a 'forced flush':

	smp_text_poke_batch_flush(NULL);

Just open-code the vector-flush in a straightforward fashion:

	smp_text_poke_batch_process(tp_vec, tp_vec_nr);
	tp_vec_nr = 0;

And get rid of !addr hack from text_poke_addr_ordered().

Leave a WARN_ON_ONCE(), just in case some external code learned
to rely on this behavior.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Juergen Gross <jgross@suse.com>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250411054105.2341982-24-mingo@kernel.org