pinctrl: mvebu: allow plat-orion architectures to use pinctrl-mvebu

The mach-kirkwood and mach-dove architectures have not yet been
integrated into the mach-mvebu directory, which should ultimately
contain the support for all Marvell SoCs from the Engineering Business
Unit.

However, before this can happen, we need to let mach-kirkwood and
mach-dove use the pinctrl-mvebu driver, which supports the kirkwood
and dove SoC families. In order to do that, we make this driver
available as soon as PLAT_ORION is selected, instead of using
ARCH_MVEBU as a condition. In the long term, PLAT_ORION should
disappear and be fully replaced by ARCH_MVEBU, but the plan is to make
the migration step by step, by first having the existing mach-*
directories for Marvell SoCs converge on several infrastructures,
including the pinctrl one.

Also, like the spear pinctrl driver, we put all pinctrl-mvebu Kconfig
options under a if, in order to avoid having certain options
(PINCTRL_DOVE, PINCTRL_KIRKWOOD, etc.) selecting an option
(PINCTLR_MVEBU) which itself has a dependency (on ARCH_MVEBU). In this
a construct, the dependency is in fact ignored due to the selects.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>