pinctrl: mvebu: fix num_settings in mpp group assignment

When assigning mpp settings from static mpp modes to mpp groups,
we do not want any groups that have no supported setting for a
specific Kirkwood variant. However, when there is at least a
single supported setting, we need to assign the number of all
settings in this mode to grp->num_settings as we are reusing
the static modes table.

Fixes: 0581b16b ("pinctrl: mvebu: complain about missing group after checking variant")
Reported-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Tested-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Cc: Gregory Clement <gregory.clement@free-electrons.com>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>