platform/x86/intel/sdsi: Combine read and write mailbox flows

platform/x86/intel/sdsi: Combine read and write mailbox flows

The current mailbox commands are either read-only or write-only and the
flow is different for each. New commands will need to send and receive
data. In preparation for these commands, create a common polling function
to handle sending data and receiving in the same transaction.

Signed-off-by: David E. Box <david.e.box@linux.intel.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20240411025856.2782476-3-david.e.box@linux.intel.com
Signed-off-by: Hans de Goede <hdegoede@redhat.com>