[bug report] drm/amd/display: Add basic infrastructure for enabling FAMS

[Dan Carpenter <dan.carpenter@xxxxxxxxxx>]

Hello Rodrigo Siqueira,

This is a semi-automatic email about new static checker warnings.

The patch 00fa7f031dd4: "drm/amd/display: Add basic infrastructure
for enabling FAMS" from Jun 16, 2022, leads to the following Smatch
complaint:

    drivers/gpu/drm/amd/amdgpu/../display/dc/dc_dmub_srv.c:311 dc_dmub_srv_p_state_delegate()
    warn: variable dereferenced before check 'dc' (see line 309)

drivers/gpu/drm/amd/amdgpu/../display/dc/dc_dmub_srv.c
   308		int ramp_up_num_steps = 1; // TODO: Ramp is currently disabled. Reenable it.
   309		uint8_t visual_confirm_enabled = dc->debug.visual_confirm == VISUAL_CONFIRM_FAMS;
                                                 ^^^^^^^^^^^^^^^^^^^^^^^^
Dereference

   310	
   311		if (dc == NULL)
                    ^^^^^^^^^^
NULL check is too late

   312			return false;
   313	

regards,
dan carpenter