RDMA/bnxt_re: wraparound mbox producer index

In the Linux kernel, the following vulnerability has been resolved:

RDMA/bnxt_re: wraparound mbox producer index

Driver is not handling the wraparound of the mbox producer index correctly.

Currently the wraparound happens once u32 max is reached.

Bit 31 of the producer index register is special and should be set

only once for the first command. Because the producer index overflow

setting bit31 after a long time, FW goes to initialization sequence

and this causes FW hang.

Fix is to wraparound the mbox producer index once it reaches u16 max.