mfd: pm8xxx: Make elegible for COMPILE_TEST

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>

drivers/mfd/Kconfig

@@ -887,7 +887,7 @@ config UCB1400_CORE
 
 config MFD_PM8XXX
 	tristate "Qualcomm PM8xxx PMIC chips driver"
-	depends on (ARM || HEXAGON)
+	depends on (ARM || HEXAGON || COMPILE_TEST)
 	select IRQ_DOMAIN
 	select MFD_CORE
 	select REGMAP