pinctrl: make the MSM SoC driver depend on OF

We had a compilation failure on x86_64 due to missing OF support
as this was an implicit dependency. Add an explicit dependency
on OF and OF_IRQ on the SoC driver.

Cc: Bjorn Andersson <bjorn.andersson@sonymobile.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
ChangeLog v2->v3:
- Total failure with older approaches: what we need to do is
  have the *SoC subdriver* depend on OF and OF_IRQ. This is
  because the placeholder bool PINCTRL_MSM cannot cascade its
  dependencies when a subdriver selects it, Kconfig is smart
  but not that smart.
ChangeLog v1->v2:
- OK so "depends on OF" did not work here let's try to simply
  select OF and OF_IRQ for this then? It's one of those
  "warning: (PINCTRL_MSM8X74) selects PINCTRL_MSM which has
  unmet direct dependencies (PINCTRL && OF)" that I simply
  cannot find my way out of :-/