The DRM DP code has macros for the DP HDCP capabilities. Use them in the
anx7625 driver instead of raw numbers.

Fixes: cd1637c7 ("drm/bridge: anx7625: add HDCP support")
Suggested-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
Reviewed-by: Robert Foss <rfoss@kernel.org>
Signed-off-by: Robert Foss <rfoss@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230710091203.1874317-1-wenst@chromium.org