net: stmmac: provide function to lookup hwif

net: stmmac: provide function to lookup hwif

Provide a function to lookup the hwif entry given the core type,
Synopsys version, and device ID (used for XGMAC cores).

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Tested-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Tested-by: Mohd Ayaan Anwar <mohd.anwar@oss.qualcomm.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://patch.msgid.link/E1vDtf6-0000000CCCL-1cQA@rmk-PC.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>