pinctrl: qcom: make 'm_voc_groups' static

pinctrl: qcom: make 'm_voc_groups' static

The m_voc_groups is not declared outside of the
driver, so make it static to avoid the following
sparse wanrning:

drivers/pinctrl/qcom/pinctrl-msm8976.c:592:12: warning: symbol 'm_voc_groups' was not declared. Should it be static?

Signed-off-by: Ben Dooks (Codethink) <ben.dooks@codethink.co.uk>
Link: https://lore.kernel.org/r/20191218102804.2487374-1-ben.dooks@codethink.co.uk
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>