mei: bus: fix hw module get/put balance

In case the device is not connected it doesn't 'get'
hw module and hence should not 'put' it on disable.

Cc: <stable@vger.kernel.org> 4.16+
Fixes:'commit 257355a4 ("mei: make module referencing local to the bus.c")'
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=200455


Tested-by: Georg Müller <georgmueller@gmx.net>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>