This should be enabled so that we get full compile coverage
of the PM8xxx MFD core with the different subdrivers.

Tested on the build servers.
Suggested-by: NJonathan Cameron <jic23@kernel.org>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: NLee Jones <lee.jones@linaro.org>