drm/amd/dc: fix semicolon.cocci warnings

Remove unneeded semicolons.

Generated by: scripts/coccinelle/misc/semicolon.cocci

Signed-off-by: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>