net: ethernet: ti: am65-cpsw-qos: Demote non-conformant function header

Fixes the following W=1 kernel build warning(s):

 drivers/net/ethernet/ti/am65-cpsw-qos.c:364: warning: Function parameter or member 'ndev' not described in 'am65_cpsw_timer_set'
 drivers/net/ethernet/ti/am65-cpsw-qos.c:364: warning: Function parameter or member 'est_new' not described in 'am65_cpsw_timer_set'

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>