BugLink: https://bugs.launchpad.net/bugs/1792174

The delta was only in comments or blank lines. So this brings the
file (arch/x86/include/asm/pgtable_64.h) into sync with 4.4.148.
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>