drm/msm: move msm_readl/_writel to msm_drv.h

drm/msm: move msm_readl/_writel to msm_drv.h

With the reglog removal, msm_readl/_writel became single line wrappers
around readl/writel. Move those two wrappers and msm_rmw to msm_drv.h to
remove need for extra function calls when doing register writes.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/20220105232700.444170-3-dmitry.baryshkov@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>