fm10k: cleanup mailbox code comments etc

fm10k: cleanup mailbox code comments etc

Cleanup a number of issues with function header comments, lower-case
acronyms (i.e. FIFO, TLV), duplicate comments and a stubbed-out header
comment for fm10k_sm_mbx_init.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Tested-by: Krishneil Singh <Krishneil.k.singh@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Orabug: 25394529
(cherry picked from commit f632fed30f8e0c1b5c9de209f00145f516e7ad37)
Signed-off-by: Jack Vogel <jack.vogel@oracle.com>