i2c: i801: Fix missing Kconfig dependency

The original change adds usage of i2c_root_adapter(), which is
implemented in i2c-mux.c. Therefore we can't use the multiplexing
if I2C_I801=y and I2C_MUX=m.
Handling the dependencies in the code would become unnecessarily
complex, therefore create a new config symbol.

Fixes: 893fef0b ("i2c: i801: Call i2c_register_spd for muxed child segments")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202404042206.MjAQC32x-lkp@intel.com/


Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>