xen/x86: remove cf_check attribute from hypercall handlers

xen/x86: remove cf_check attribute from hypercall handlers

Now that the hypercall handlers are all being called directly instead
through a function vector, the "cf_check" attribute can be removed.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Daniel P. Smith <dpsmith@apertussolutions.com> # xsm parts
Acked-by: Jan Beulich <jbeulich@suse.com>
Tested-by: Téo Couprie Diaz <teo.coupriediaz@arm.com>
Acked-by: Dario Faggioli <dfaggioli@suse.com>