pinctrl: qcom: Use platform_irq_count() instead of of_irq_count()

of_irq_count() is not an exported symbol (and it shouldn't be
used by platform drivers anyway) so use platform_irq_count()
instead. This allows us to make the qcom pinctrl drivers modular
again.

Cc: Rob Herring <robh+dt@kernel.org>
Cc: Andy Gross <andy.gross@linaro.org>
Cc: Bjorn Andersson <bjorn@kryo.se>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>