net: lan743x: Remove unused argument in lan743x_common_regs( )

Remove the unused argument (i.e. struct ethtool_regs *regs) in
lan743x_common_regs( ) function arguments.

Signed-off-by: Raju Lakkaraju <Raju.Lakkaraju@microchip.com>
Reviewed-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>