x86: don't apply reboot quirks if reboot set by user

x86: don't apply reboot quirks if reboot set by user

If reboot= is specified on the command-line, don't apply reboot quirks
to allow the command-line option to take precedence.

This is a port of Linux commit 5955633e91bf ("x86/reboot: Skip DMI
checks if reboot set by user").

Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
Leverage (and make apply on top of) c643fb110a ("x86/EFI: allow
reboot= overrides when running under EFI").

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>