net: phy: dp83867: Fix SGMII FIFO depth for non OF devices

Current driver code will read device tree node information,
and set default values if there is no info provided.

This is not done in non-OF devices leading to SGMII fifo depths being
set to the smallest size.

This patch sets the value to the default value of the PHY as stated in the
PHY datasheet.

Fixes: 4dc08dcc

 ("net: phy: dp83867: introduce critical chip default init for non-of platform")
Signed-off-by: Michael Sit Wei Hong <michael.wei.hong.sit@intel.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/20221110054938.925347-1-michael.wei.hong.sit@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>