drm: Introduce 'power saving policy' drm property

drm: Introduce 'power saving policy' drm property

The `power saving policy` DRM property is an optional property that
can be added to a connector by a driver.

This property is for compositors to indicate intent of policy of
whether a driver can use power saving features that may compromise
the experience intended by the compositor.

Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240703051722.328-2-mario.limonciello@amd.com