staging/mei: fix failure for multiple mei clients connection

The irq handler processes queued mei clients connect requests, which were
not transferred to the device in ioctl context due to unavailability
of the write buffer.

The handler may transfer the connection request only if there is
no other ongoing  requests for the same mei id.
This condition was implemented inversely which depending on
the write buffer availability lead to seemingly random
failures during connection attempts.

Cc: Oren Weil <oren.jer.weil@intel.com>
Signed-off-by: Natalia Ovsyanikov <natalia.ovsyanikov@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>