drm/amd/display: Fix failure to read vram info due to static BP_RESULT

The static declaration causes the check to fail.  Remove it.

Closes: drm/amd#3678


Fixes: 00c39110 ("drm/amd/display: Add misc DC changes for DCN401")
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Hamish Claxton <hamishclaxton@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: aurabindo.pillai@amd.com
Cc: hamishclaxton@gmail.com