dz: update kconfig description

Reformat the Kconfig entries and update descriptions for accuracy.  Select the
driver by default for configurations of interest.  For the curious: 32BIT
means only 32-bit DECstations support the device, not that the driver is not
64-bit clean; I have not checked that either though.

Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Cc: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>