[PATCH] Avoid use of uninitialised spinlock in EEH.

If the kernel supports both G5 and pSeries, and CONFIG_EEH is enabled,
eeh_init() is (quite reasonably) never called when we boot on a G5. Yet
eeh_check_failure() still gets called. We should avoid doing that if
!eeh_subsystem_enabled.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>