drm/amd: Beef up ACP Kconfig menu text

The current "text" needs a user to use a crystal ball in order to find
out what this ACP thing is.

Use the text from

  a8fe58ce ("drm/amd: add ACP driver support")

to make it a bit more understandable to the rest of the world.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Chunming Zhou <david1.zhou@amd.com>
Cc: Jammy Zhou <Jammy.Zhou@amd.com>
Cc: Maruthi Bayyavarapu <maruthi.bayyavarapu@amd.com>
Cc: Murali Krishna Vemuri <murali-krishna.vemuri@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>