pinctrl: msm: Make number of functions variable

The various pins may have different number of functions defined, so make this
number definable per pin instead of just increasing it to the largest one for
all of the platforms.

Signed-off-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>