hv_netvsc: make const array ver_list static, reduces object code size

Don't populate const array ver_list on the stack, instead make it
static. Makes the object code smaller by over 400 bytes:

Before:
   text	   data	    bss	    dec	    hex	filename
  18444	   3168	    320	  21932	   55ac	drivers/net/hyperv/netvsc.o

After:
   text	   data	    bss	    dec	    hex	filename
  17950	   3224	    320	  21494	   53f6	drivers/net/hyperv/netvsc.o

(gcc 6.3.0, x86-64)

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>