x86/mm: Use INVLPGB for kernel TLB flushes

Use broadcast TLB invalidation for kernel addresses when available.
Remove the need to send IPIs for kernel TLB flushes.

   [ bp: Integrate dhansen's comments additions, merge the
     flush_tlb_all() change into this one too. ]

Signed-off-by: Rik van Riel <riel@surriel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20250226030129.530345-5-riel@surriel.com