staging/mei: refactor mei_wd_host_init function

The function has returned false in both error and success
cases.

1. change return value to int and return appropriate errno
2. use typical Linux kernel error handling.
3. normalize debug messages

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>