x86/mm/tlb: Unify flush_tlb_func_local() and flush_tlb_func_remote()

The unification of these two functions allows to use them in the updated
SMP infrastrucutre.

To do so, remove the reason argument from flush_tlb_func_local(), add
a member to struct tlb_flush_info that says which CPU initiated the
flush and act accordingly. Optimize the size of flush_tlb_info while we
are at it.

Unfortunately, this prevents us from using a constant tlb_flush_info for
arch_tlbbatch_flush(), but in a later stage we may be able to inline
tlb_flush_info into the IPI data, so it should not have an impact
eventually.

Signed-off-by: Nadav Amit <namit@vmware.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/r/20210220231712.2475218-3-namit@vmware.com