drm/amd/display: Fix warning for analog stream encoders

drm/amd/display: Fix warning for analog stream encoders

Fixes the following warning that some users are reporting
with some kernel configurations:

"positional initialization of field in 'struct' declared
with 'designated_init' attribute"

Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Acked-by: Kees Cook <kees@kernel.org>
Link: https://lore.kernel.org/r/20251113163348.137315-2-timur.kristof@gmail.com
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>