net: txgbe: Fix I2C Kconfig dependencies

net: txgbe: Fix I2C Kconfig dependencies

The dependency handling of the Synopsys DesignWare I2C
adapter drivers is going to be changed so that the glue
drivers for the platform and PCI buses depend on
I2C_DESIGNWARE_CORE. Right now this driver prevents that
update because it selects I2C_DESIGNWARE_PLATFORM.

To make the dependency on I2C_DESIGNWARE_PLATFORM consistent
with the other drivers in kernel that depend on it, and
allow the dependency handling of the Synopsys DesignWare I2C
drivers to be updated, change the "select" into "depends on".

Cc: Jiawen Wu <[email protected]>
Cc: Mengyuan Lou <[email protected]>
Cc: David S. Miller <[email protected]>
Cc: Eric Dumazet <[email protected]>
Cc: Jakub Kicinski <[email protected]>
Cc: Paolo Abeni <[email protected]>
Cc: [email protected]
Signed-off-by: Heikki Krogerus <[email protected]>
Acked-by: Jarkko Nikula <[email protected]>
Signed-off-by: Andi Shyti <[email protected]>