m68k/mac: Replace via-maciisi driver with via-cuda driver

Change the device probe test in the via-cuda.c driver so it will load on
Egret-based machines too. Remove the now redundant via-maciisi.c driver.

Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>