drm/radeon/si: Fix inconsistent indenting

Kernel test robot throws below warning ->

smatch warnings:
drivers/gpu/drm/radeon/si.c:4514 si_vm_packet3_cp_dma_check() warn:
inconsistent indenting

Fixed the inconsistent indenting.
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>