x86/HVM: re-order operations in hvm_ud_intercept()

x86/HVM: re-order operations in hvm_ud_intercept()

Don't fetch CS explicitly, leverage the fact that hvm_emulate_prepare()
already does (and that hvm_virtual_to_linear_addr() doesn't alter it).

At once increase the length passed to hvm_virtual_to_linear_addr() by
one: There definitely needs to be at least one more opcode byte, and we
can avoid missing a wraparound case this way.

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