mfd: Add Cherry Trail Whiskey Cove PMIC driver

Add mfd driver for Intel CHT Whiskey Cove PMIC, based on various non
upstreamed CHT Whiskey Cove PMIC patches.

This is a somewhat minimal version which adds irqchip support and cells
for: ACPI PMIC opregion support, the i2c-controller driving the external
charger irc and the pwrsrc/extcon block.

Further cells can be added in the future if/when drivers are upstreamed
for them.

[The above patch caused a build error on some archetectures]

From: Arnd Bergmann <arnd@arndb.de>

I ran into a build error on ARM with a platform that has a non-standard
clk implementation:

drivers/clk/clk.o: In function `clk_disable':
clk.c:(.text.clk_disable+0x0): multiple definition of `clk_disable'
arch/arm/mach-omap1/clock.o:clock.c:(.text.clk_disable+0x0): first defined here
drivers/clk/clk.o: In function `clk_enable':
clk.c:(.text.clk_enable+0x0): multiple definition of `clk_enable'
arch/arm/mach-omap1/clock.o:clock.c:(.text.clk_enable+0x0): first defined here

The problem is a device driver that uses 'select COMMON_CLK', which is
generally a bad idea: selecting a subsystem should only be done from
a platform, otherwise we run into circular dependencies. The same driver
also selects 'GPIOLIB' and 'I2C', which has a similar effect.

This turns all three into 'depends on', as it should be.

Finally, we can limit the build to x86, unless we are compile testing.

First patch:
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

Fix for first patch (squashed):
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>