mb/lenovo/x200/blc: Add LTD121EQ3B panel at 447Hz

Change-Id: Ia44097f32f74ffd749219415984224ce33d9252b
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/19816
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

src/mainboard/lenovo/x200/blc.c

@@ -18,6 +18,8 @@
 #include <northbridge/intel/gm45/gm45.h>
 
 static const struct blc_pwm_t blc_entries[] = {
+	/* corrected to 320MHz CDClk, vendor set 753; works fine at both: */
+	{"LTD121EQ3B", 447},
 	{"LTD121EWVB", 165},
 	{"B121EW03 V6 ", 165},
 	/* datasheets: between 100 and 20k, typical 200 */