[PARISC] Fix mux.c driver

Missing spin_lock_init() made the Mux driver hang on SMP systems.

Fix up users of ->hpa to use ->hpa.start instead

Remove warning in 8250_gsc.c by eliminating serial_line_nr

Signed-off-by: Matthew Wilcox <willy@parisc-linux.org>

Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>