IB/rdmavt: rdmavt_qp.h: clean up kernel-doc comments

IB/rdmavt: rdmavt_qp.h: clean up kernel-doc comments

Correct the kernel-doc comments format to avoid around 35 kernel-doc
warnings:

- use struct keyword to introduce struct kernel-doc comments
- use correct variable name for some struct members
- use correct function name in comments for some functions
- fix spelling in a few comments
- use a ':' instead of '-' to separate struct members from their
  descriptions
- add a function name heading for rvt_div_mtu()

This leaves one struct member that is not described:
rdmavt_qp.h:206: warning: Function parameter or struct member 'wq'
 not described in 'rvt_krwq'

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://patch.msgid.link/20251105045127.106822-1-rdunlap@infradead.org
Signed-off-by: Leon Romanovsky <leon@kernel.org>