Documentation/gpu: remove duplicate entries in different glossaries

Some items were defined in both the general and DC glossaries.
Remove the duplicate entries.

Fixes: 2df30ae0 ("Documentation/gpu: Add acronyms for some firmware components")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Rodrigo Siqueira <siqueira@igalia.com>
Reviewed-by: Rodrigo Siqueira <siqueira@igalia.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>