Documentation/gpu: Expand generic block information

Documentation/gpu: Expand generic block information

This commit expands the overall explanation about AMD GPU IPs by adding
more details about their interconnection. Note that this commit includes
a diagram that provides additional information.

v2: fix up TMR - Trusted Memory Region

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