Move csr reading into me hardware functional calls.
Since we gave up on registers caching we remove some of the unnecessary
queries in mei_hw_init ane mei_reset functions.

We add mei_hw_config function to wrap up host buffer depth configuration.
Signed-off-by: NTomas Winkler <tomas.winkler@intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>