Sometimes mailbox commands timeout when the RX data path becomes
unresponsive. This prevents the submission of new mailbox commands to DXIO.
This patch identifies the timeout and resets the RX data path so that the
next message can be submitted properly.

Fixes: 549b32af ("amd-xgbe: Simplify mailbox interface rate change code")
Co-developed-by: Sudheesh Mavila <sudheesh.mavila@amd.com>
Signed-off-by: Sudheesh Mavila <sudheesh.mavila@amd.com>
Signed-off-by: Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
Acked-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: David S. Miller <davem@davemloft.net>