Documentation/gpu: Add new glossary entries from UMR

Documentation/gpu: Add new glossary entries from UMR

When using UMR, a dashboard is available that displays the CPC, CPF,
CPG, TCP, and UTCL utilization. This commit introduces the meanings of
those acronyms (and others) to the glossary to improve the comprehension
of the UMR dashboard.

Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Timur Kristóf <timur.kristof@gmail.com>
Cc: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Rodrigo Siqueira <siqueira@igalia.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>