Fix the reading of the cylinder start/end pressure from cylinder models

Fix the reading of the cylinder start/end pressure from cylinder models

The cylinder model doesn't contain the start/end pressures, they just
contain the cylinder type information.  So trying to read the start and
end pressure from the cylinder model change callback is totally bogus.

We need to set the start/end pressures from the cylinder info when we
create the cylinder widget, and not touch them when the type changes.
So split up the "set_cylinder_spinbuttons()" function in two: one that
sets the type information, and one that sets the start/end pressure.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>