hw/intc/arm_gicv3_common: Move gicd shift bug handling to gicv3_post_load

The code currently in gicv3_gicd_no_migration_shift_bug_post_load()
that handles migration from older QEMU versions with a particular
bug is misplaced. We need to run this after migration in all cases,
not just the cases where the "arm_gicv3/gicd_no_migration_shift_bug"
subsection is present, so it must go in a post_load hook for the
top level VMSD, not for the subsection. Move it.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-id: 20180806123445.1459-6-peter.maydell@linaro.org