spapr: Clean up LPCR updates from hypercalls

spapr: Clean up LPCR updates from hypercalls

There are several places in spapr_hcall.c where we need to update the LPCR
value on all CPUs.  We do this with the set_spr() helper.  That's not
really correct because this directly sets the SPR value, without going
through the ppc_store_lpcr() helper which may need to update state based
on the LPCR change.

In fact, set_spr() is only ever used for the LPCR, so replace it with an
explicit LPCR updated which uses the right low-level helper.  While we're
there, move the CPU_FOREACH() which was in every one of the callers into
the new helper: set_all_lpcrs().

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Tested-by: Cédric Le Goater <clg@kaod.org>