net: stmmac: use FIELD_GET() for version register

net: stmmac: use FIELD_GET() for version register

Provide field definitions in common.h, and use these with FIELD_GET()
to extract the fields from the version register.

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/E1vDtf1-0000000CCCF-0uUV@rmk-PC.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>