powerpc: hv{cs, si}_close() both unsigned hp->count and hvcsd->open_count cannot be negative

[Paul Mackerras]

Alan Cox writes:

> See the tty_port patches in -next - this is an argument about code which
> ought eventually to go away replaced by standard helper functions.

OK.  In that case I think the best fix for the existing code is just
to change the count to be int rather than unsigned int.

Paul.