Documentation/x86: Fix backwards on/off logic about YMM support

commit 1b0fc0345f2852ffe54fb9ae0e12e2ee69ad6a20 upstream

These options clearly turn *off* XSAVE YMM support.  Correct the
typo.

Reported-by: Ben Hutchings <ben@decadent.org.uk>
Fixes: 553a5c03e90a ("x86/speculation: Add force option to GDS mitigation")
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>