x86emul: suppress alignment check for {,v}mov{d,q}

When introducing support for these instructions, adjustment for the
alignment check logic (generating #GP(0)) was overlooked.

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

xen/arch/x86/x86_emulate/x86_emulate.c

@@ -4940,7 +4940,7 @@ x86_emulate(
         {
             uint32_t mxcsr = 0;
 
-            if ( vex.pfx != vex_66 )
+            if ( ea.bytes < 16 || vex.pfx == vex_f3 )
                 mxcsr = MXCSR_MM;
             else if ( vcpu_has_misalignsse() )
                 asm ( "stmxcsr %0" : "=m" (mxcsr) );