In rev. 1.156, the convertion of the minor number to the unit number resulted in the argument to the make_dev() to be a unit number.
In rev. 1.156, the convertion of the minor number to the unit number
resulted in the argument to the make_dev() to be a unit number.

Correct this by supplying a minor number to make_dev(), and using
the unit number for the calculation of the slave tty name.

Reported and tested by:	Peter Holm
Reviewed by:	jhb
Yet another pointy hat to:	kib
MFC after:	1 day

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase