drm/amdgpu: fix inconsistent indenting warning

Fix below inconsistent indenting smatch warning.
smatch warnings:
drivers/gpu/drm/amd/amdgpu/amdgpu_sdma.c:582 amdgpu_sdma_reset_engine() warn: inconsistent indenting

Signed-off-by: Charles Han <hanchunchao@inspur.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>