net: dsa: b53: unexport and move b53_eee_enable_set()

After commit f86ad77f ("net: dsa: bcm_sf2: Utilize b53_{enable,
disable}_port"), bcm_sf2.c no longer calls b53_eee_enable_set(), and all
its callers are in b53_common.c.

We also need to move it, because it is called within b53_common.c before
its definition, and we want to avoid forward declarations.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Acked-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://lore.kernel.org/r/20240206112527.4132299-1-vladimir.oltean@nxp.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>