drm/radeon: check that we have a clock before PLL setup

Partially fixes: https://bugzilla.kernel.org/show_bug.cgi?id=75211

Signed-off-by: Christian König <christian.koenig@amd.com>

drivers/gpu/drm/radeon/atombios_crtc.c

@@ -1901,6 +1901,9 @@ int atombios_crtc_mode_set(struct drm_crtc *crtc,
 	    (ATOM_DEVICE_TV_SUPPORT | ATOM_DEVICE_CV_SUPPORT))
 		is_tvcv = true;
 
+	if (!radeon_crtc->adjusted_clock)
+		return -EINVAL;
+
 	atombios_crtc_set_pll(crtc, adjusted_mode);
 
 	if (ASIC_IS_DCE4(rdev))