At the moment, all 5 I2C and 6 SPI buses are probed and exposed
to user-space by default - even if they are not muxed to any pins
on the board. This means that user-space sees an I2C/SPI bus that
cannot be actually used properly.

In some cases this was used to put the corresponding pins into
a low power sleep mode - but even then the pins first need to be
configured by the board-specific device tree part.

Avoid exposing unconfigured devices to user-space by disabling
the I2C/SPI buses by default. Enable them in the board device trees
when needed.
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Link: https://lore.kernel.org/r/20191125170428.76069-1-stephan@gerhold.netSigned-off-by: Linus Walleij <linus.walleij@linaro.org>