spapr: Set compatibility mode before the rest of spapr_cpu_reset()

spapr: Set compatibility mode before the rest of spapr_cpu_reset()

Although the order doesn't really matter at the moment, it's possible
other initializastions could depend on the compatiblity mode, so make sure
we set it first in spapr_cpu_reset().

While we're at it drop the test against first_cpu.  Setting the compat mode
to the value it already has is redundant, but harmless, so we might as well
make a small simplification to the code.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Greg Kurz <groug@kaod.org>