drm/amd: Fix UBSAN array-index-out-of-bounds for SMU7

[ Upstream commit 760efbca74a405dc439a013a5efaa9fadc95a8c3 ]

For pptable structs that use flexible array sizes, use flexible arrays.

Suggested-by: Felix Held <felix.held@amd.com>
Link: https://gitlab.freedesktop.org/drm/amd/-/issues/2874


Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>