net: dsa: sja1105: fix device id detection

The sja1105_check_device_id() function contains logic to work without
changing the device tree on reworked boards, one of which I have (the
NXP LS1021A-TSN normally has a SJA1105T, but I have a version with a
resoldered SJA1105Q which is pin compatible). This logic is taken from
the Linux driver.

However this logic gets shortcircuited in U-Boot by an earlier check for
the exact device ID specified in the device tree. So the reworked board
does not probe the SJA1105Q switch. Remove this duplicated logic and let
the automatic device ID detection do its job.

Fixes: f24b666b ("net: dsa: add driver for NXP SJA1105 L2 switch")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>