vt: synchronize types and use min in csi_X

All the types are unsinged ints -- even the vpar passed to the function.
So unify them and use min() to compute count instead of explicit
comparison.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20200615074910.19267-23-jslaby@suse.cz


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>