x86/mm/64: Do not sync vmalloc/ioremap mappings

Remove the code to sync the vmalloc and ioremap ranges for x86-64. The
page-table pages are all pre-allocated so that synchronization is
no longer necessary.

This is a patch that already went into the kernel as:

	commit 8bb9bf24 ("x86/mm/64: Do not sync vmalloc/ioremap mappings")

But it had to be reverted later because it unveiled a bug from:

	commit 6eb82f99 ("x86/mm: Pre-allocate P4D/PUD pages for vmalloc area")

The bug in that commit causes the P4D/PUD pages not to be correctly
allocated, making the synchronization still necessary. That issue got
fixed meanwhile upstream:

	commit 995909a4 ("x86/mm/64: Do not dereference non-present PGD entries")

With that fix it is safe again to remove the page-table synchronization
for vmalloc/ioremap ranges on x86-64.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200814151947.26229-2-joro@8bytes.org