mfd: simple-mfd-i2c: Add Delta TN48M CPLD support

mfd: simple-mfd-i2c: Add Delta TN48M CPLD support

Delta TN48M switches have a Lattice CPLD that serves
multiple purposes including being a GPIO expander.

So, lets use the simple I2C MFD driver to provide the MFD core.

Also add a virtual symbol which pulls in the simple-mfd-i2c driver and
provide a common symbol on which the subdevice drivers can depend on.

Acked-for-MFD-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Robert Marko <robert.marko@sartura.hr>
Link: https://lore.kernel.org/r/20220131133049.77780-2-robert.marko@sartura.hr
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>