drm/nouveau/bios/dp: make array vsoff static, shrinks object size

drm/nouveau/bios/dp: make array vsoff static, shrinks object size

Don't populate the array vsoff on the stack but instead make it
static. Makes the object code smaller by 67 bytes:

Before:
   text	   data	    bss	    dec	    hex	filename
   5753	    112	      0	   5865	   16e9	.../nouveau/nvkm/subdev/bios/dp.o

After:
   text	   data	    bss	    dec	    hex	filename
   5622	    176	      0	   5798	   16a6	.../nouveau/nvkm/subdev/bios/dp.o

(gcc version 8.2.0 x86_64)

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>