x86/xstate: undo bogus adjustment to xsave()

This reverts an unintended change in commit 879b44b041 ("x86/fpu: add
a per-domain field to set the width of FIP/FDP"), which I had done
intermediately while fixing the build issue: After having reverted that
adjustment I must have forgotten to "git add" the adjustment.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/xstate.c
+++ b/xen/arch/x86/xstate.c
@@ -292,7 +292,7 @@ void xsave(struct vcpu *v, uint64_t mask)
 
         XSAVE("0x48,");
 
-        if ( !(ptr->xsave_hdr.xstate_bv & XSTATE_FP) ||
+        if ( !(mask & ptr->xsave_hdr.xstate_bv & XSTATE_FP) ||
              /*
               * AMD CPUs don't save/restore FDP/FIP/FOP unless an exception
               * is pending.