net: stmmac: Fix EST offset for dwmac 5.10

Fix EST offset for dwmac 5.10.

Currently configuring Qbv doesn't work as expected. The schedule is
configured, but never confirmed:

|[  128.250219] imx-dwmac 428a0000.ethernet eth1: configured EST

The reason seems to be the refactoring of the EST code which set the wrong
EST offset for the dwmac 5.10. After fixing this it works as before:

|[  106.359577] imx-dwmac 428a0000.ethernet eth1: configured EST
|[  128.430715] imx-dwmac 428a0000.ethernet eth1: EST: SWOL has been switched

Tested on imx93.

Fixes: c3f3b972 ("net: stmmac: Refactor EST implementation")
Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>
Reviewed-by: Serge Semin <fancer.lancer@gmail.com>
Link: https://lore.kernel.org/r/20240220-stmmac_est-v1-1-c41f9ae2e7b7@linutronix.de


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