drm/amdgpu/vcn: Remove redundant indirect SRAM HW model check

The HW model validation that guards the indirect SRAM checking in the
VCN code path is redundant - there's no model that's not included in the
switch, making it useless in practice [0].

So, let's remove this switch statement for good.

[0] lore.kernel.org/amd-gfx/MN0PR12MB61013D20B8A2263B22AE1BCFE2C19@MN0PR12MB6101.namprd12.prod.outlook.com

Suggested-by: Alex Deucher <Alexander.Deucher@amd.com>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Cc: James Zhu <James.Zhu@amd.com>
Cc: Lazar Lijo <Lijo.Lazar@amd.com>
Cc: Leo Liu <leo.liu@amd.com>
Cc: Sonny Jiang <sonny.jiang@amd.com>
Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>