drm/msm/dp: move I/O functions to global header

Move msm_dp_read()/msm_write_foo() functions to the dp_catalog.h,
allowing other modules to access the data directly.

Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Tested-by: Stephen Boyd <swboyd@chromium.org> # sc7180-trogdor
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/654318/
Link: https://lore.kernel.org/r/20250518-fd-dp-audio-fixup-v6-4-2f0ec3ec000d@oss.qualcomm.com