block/DAC960.c: make some arrays static const, shrinks object size

Don't populate the arrays ReadCacheStatus, WriteCacheStatus and
SenseErrors on the stack but instead make them static const. Makes
the object code smaller by 47 bytes:

Before:
   text	   data	    bss	    dec	    hex	filename
 160974	  34628	    832	 196434	  2ff52	drivers/block/DAC960.o

After:
   text	   data	    bss	    dec	    hex	filename
 160671	  34884	    832	 196387	  2ff23	drivers/block/DAC960.o

(gcc version 8.2.0 x86_64)

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>