x86: hpet: Fix inverted return value check in arch_setup_hpet_msi()

setup_hpet_msi_remapped() returns a negative error indicator on error
- check for this rather than for a boolean false indication, and pass
on that error code rather than a meaningless "-1".

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Link: http://lkml.kernel.org/r/5093E00D02000078000A60E2@nat28.tlf.novell.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>