TTY: serialP, remove unused material

First, remove unused macro and rs_multiport_struct structure. Nobody
uses them at all.

Further, the 2 drivers (they are below) which use the rest of
structures from serialP.h (async_struct and serial_state) do not use
all the members. Remove the members:
* which are unused or
* which are only initialized and never used for something real.

Everybody should avoid the structures with a looong distance.

Finally, remove the ALPHA kludge MCR quirks. They are 1:1 copy from
8250.h. No need to redefine them here.

The 2 promised users of the structures:
arch/ia64/hp/sim/simserial.c
drivers/tty/amiserial.c

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>