drm/i915/dp_mst: Remove stream count assert from intel_dp_check_mst_status()

There doesn't seem to be a reason to assert for a non-negative stream
counter in intel_dp_check_mst_status() in particular, remove it. There
is now an equivalent assert in intel_dp_mst_dec_active_streams().

Reviewed-by: Jani Nikula <[e-mail]>
Signed-off-by: Imre Deak <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/gpu/drm/i915/display/intel_dp.c

···
 	bool link_ok = true;
 	bool reprobe_needed = false;
 
-	drm_WARN_ON_ONCE(display->drm, intel_dp->mst.active_links < 0);
-
 	for (;;) {
 		u8 esi[4] = {};
 		u8 ack[4] = {};