x86/mm: Add INVLPGB support code

Add helper functions and definitions needed to use broadcast TLB
invalidation on AMD CPUs.

  [ bp:
      - Cleanup commit message
      - Improve and expand comments
      - push the preemption guards inside the invlpgb* helpers
      - merge improvements from dhansen
      - add !CONFIG_BROADCAST_TLB_FLUSH function stubs because Clang
	can't do DCE properly yet and looks at the inline asm and
	complains about it getting a u64 argument on 32-bit code ]

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/20250226030129.530345-4-riel@surriel.com