clk: qcom: nsscc-qca8k: Fix the MDIO functions undefined issue

The clock controller driver of QCA8K depends on MDIO_BUS because
of mdio_module_driver used to register the driver.

This patch fixes the following undefined symbols.
ERROR: modpost: "mdio_driver_register"
[drivers/clk/qcom/nsscc-qca8k.ko] undefined!
ERROR: modpost: "mdio_driver_unregister"
[drivers/clk/qcom/nsscc-qca8k.ko] undefined!
ERROR: modpost: "__mdiobus_write"
[drivers/clk/qcom/nsscc-qca8k.ko] undefined!
ERROR: modpost: "__mdiobus_read"
[drivers/clk/qcom/nsscc-qca8k.ko] undefined!

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202406161634.B27sOs8B-lkp@intel.com/
Closes: https://lore.kernel.org/oe-kbuild-all/202406162047.QkUMa2fG-lkp@intel.com/


Signed-off-by: Luo Jie <quic_luoj@quicinc.com>
Link: https://lore.kernel.org/r/20240617093806.3461165-1-quic_luoj@quicinc.com


Signed-off-by: Bjorn Andersson <andersson@kernel.org>