x86/paravirt: Prevent redefinition of SAVE_FLAGS macro

The PARAVIRT_XXL changes introduced a redefinition of SAVE_FLAGS under
certain configurations. Cure it

Fixes: 6da63eb2 ("x86/paravirt: Move the pv_irq_ops under the PARAVIRT_XXL umbrella").
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: hpa@zytor.com
Link: https://lkml.kernel.org/r/20180905053720.13710-1-jgross@suse.com