cxgb4: fix usage of uninitialized variable

drivers/net/ethernet/chelsio/cxgb4/cxgb4_main.c: In function ‘init_one’:
drivers/net/ethernet/chelsio/cxgb4/cxgb4_main.c:4579:8: warning: ‘chip’ may be used uninitialized in this function [-Wmaybe-uninitialized]
   chip |= CHELSIO_CHIP_CODE(CHELSIO_T4, pl_rev);
        ^
drivers/net/ethernet/chelsio/cxgb4/cxgb4_main.c:4571:11: note: ‘chip’ was declared here
  int ver, chip;
           ^

Fixes: d86bd29e ("cxgb4/cxgb4vf: read the correct bits of PL Who Am I register")
Signed-off-by: Francois Romieu <romieu@fr.zoreil.com>
Cc: Hariprasad Shenai <hariprasad@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>