x86/svm: Don't use vmcb->tlb_control as if it is a boolean

x86/svm: Don't use vmcb->tlb_control as if it is a boolean

svm_asid_handle_vmrun() treats tlb_control as if it were boolean, but this has
been superseded by new additions to the SVM spec.

Introduce an enum containing all legal values, and update
svm_asid_handle_vmrun() to use appropriate constants.

While adjusting this, take the opportunity to fix up two coding style issues,
and trim the include list.

No functional change.

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