fbnic: Pull fbnic_fw_xmit_cap_msg use out of interrupt context

This change pulls the call to fbnic_fw_xmit_cap_msg out of
fbnic_mbx_init_desc_ring and instead places it in the polling function for
getting the Tx ready. Doing that we can avoid the potential issue with an
interrupt coming in later from the firmware that causes it to get fired in
interrupt context.

Fixes: 20d2e88c ("eth: fbnic: Add initial messaging to notify FW of our presence")
Signed-off-by: Alexander Duyck <alexanderduyck@fb.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/174654721876.499179.9839651602256668493.stgit@ahduyck-xeon-server.home.arpa


Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>