Fix bug in the error code path when bnxt_request_irq() returns failure.
bnxt_disable_napi() should not be called in this error path because
NAPI has not been enabled yet.

Fixes: c0c050c5 ("bnxt_en: New Broadcom ethernet driver.")
Signed-off-by: NVikas Gupta <vikas.gupta@broadcom.com>
Signed-off-by: NMichael Chan <michael.chan@broadcom.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>