x86/HPET: fix initialization order

x86/HPET: fix initialization order

At least the legacy path can enter its interrupt handler callout while
initialization is still in progress - that handler checks whether
->event_handler is non-NULL, and hence all other initialization must
happen before setting this field.

Do the same to the MSI initialization just in case (and to keep the
code in sync).

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Acked-by: Wei Gang <gang.wei@intel.com>
xen-unstable changeset:   23030:87aa1277eae0
xen-unstable date:        Sat Mar 12 13:19:02 2011 +0000