mei: hbm: add new error code MEI_CL_CONN_NOT_ALLOWED

The device can return error 5 (NOT_ALLOWED) on connection attempt.
This error can happen if:
1. An another connection attempt is in progress
2. There is an attempt to connect a fixed (connectionless) client
3. The number of available connections is exceeded (new in HBM 2.0)

We should not hit that error unless there is an internal book keeping
hiccup except option (3), therefore we translate the error code
to errno EBUSY;

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