board/solidrun/clearfog_gt_8k: fix auto-load of dsa driver

board/solidrun/clearfog_gt_8k: fix auto-load of dsa driver

Commit 5facee5cc32b ("configs/solidrun_clearfog_gt_8k: bump versions of
BSP components") broke automatic load of the mv88e6xxx dsa driver. The
kernel configuration makes the driver a module, which is not loaded
automatically at boot. Mark mv88e6xxx dependencies built-it to fix that.

Cc: Sergey Matyukevich <geomatsi@gmail.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Reviewed-by: Sergey Matyukevich <geomatsi@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>