stmmac: pci: Adjust IOT2000 matching

Since there are more IOT2040 variants with identical hardware but
different asset tags, the asset tag matching should be adjusted to
support them.

For the board name "SIMATIC IOT2000", currently there are 2 types of
hardware, IOT2020 and IOT2040. The IOT2020 is identified by its unique
asset tag. Match on it first. If we then match on the board name only,
we will catch all IOT2040 variants. In the future there will be no other
devices with the "SIMATIC IOT2000" DMI board name but different
hardware.

Signed-off-by: Su Bao Cheng <baocheng.su@siemens.com>
Reviewed-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: David S. Miller <davem@davemloft.net>