wifi: rsi: Remove an unused field in struct rsi_debugfs

dfs_get_ops has apparently never been used since its introduction by
commit dad0d04f ("rsi: Add RS9113 wireless driver") in 2014-03.

More-over struct rsi_dbg_ops is not defined.

Remove the unused field from struct rsi_debugfs.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://patch.msgid.link/15b0609d7b1569ec6c500a175caef4c9189f33e2.1725394207.git.christophe.jaillet@wanadoo.fr