net: stmmac: simplify stmmac_get_version()

net: stmmac: simplify stmmac_get_version()

We can simplify stmmac_get_version() by pre-initialising the version
members to zero, detecting the MAC100 core and returning, otherwise
determining the version register offset separately from calling
stmmac_get_id() and stmmac_get_dev_id(). Do this.

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/E1vDtel-0000000CCBx-3Lpf@rmk-PC.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>