net/bnx2x: check return codes during VF mailbox operation
net/bnx2x: check return codes during VF mailbox operation

Refactor bnx2x_do_req4pf() to be easier to read and return errors when
the transaction fails -- Previously, it could succeed when the control
channel was down.

Fixes: 540a211084a7 ("bnx2x: driver core")

Signed-off-by: Chas Williams <921b14f935223b321d369dedbe14228440f895fd@gmail.com>
Acked-by: Harish Patil <011828aa8c6d8759d925e6e8880645d7f6744b56@qlogic.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk