x86/compat: correct SMEP/SMAP NOPs patching

x86/compat: correct SMEP/SMAP NOPs patching

Correct the number of single byte NOPs we want to be replaced in case
neither SMEP nor SMAP are available.

Also simplify the expression adding these NOPs - at that location .
equals .Lcr4_orig, and removing that part of the expression fixes a
bogus ".space or fill with negative value, ignored" warning by very old
gas (which actually is what made me look at those constructs again).

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Release-acked-by: Wei Liu <wei.liu2@citrix.com>