staging: comedi: drivers: re-do macros for PLX PCI 9080 LASxBA values

Replace the existing macros in "plx9080.h" that define values for the
LAS0BA and LAS1BA registers.  Use the prefix `PLX_LASBA_` for the
macros.  Make use of the `BIT(x)` and `GENMASK(h,l)` macros to define
the macros.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>