lenovo/t440p: fix keyboard backlight

It is found that keyboard backlight in T440p is enabled by clearing
bit 3 of EC RAM 0x01. This patch sets has_keyboard_backlight in
devicetree.cb and also corrects the CMOS configuration.

Change-Id: Ib4c2b1591d26e2bb33f9549e3933efe9a6e0b043
Signed-off-by: Iru Cai <mytbk920423@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/38650
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Dennis Witzig <dennis@wtzg.de>
Reviewed-by: Alexander Couzens <lynxis@fe80.eu>

src/mainboard/lenovo/t440p/cmos.default

@@ -9,5 +9,5 @@ fn_ctrl_swap=Disable
 f1_to_f12_as_primary=Enable
 sticky_fn=Disable
 trackpoint=Enable
-backlight=Both
+backlight=Keyboard
 usb_always_on=Disable

src/mainboard/lenovo/t440p/cmos.layout

@@ -103,9 +103,10 @@ enumerations
 8     1     Primary
 9     0     AHCI
 9     1     Compatible
-10    0     Both
-10    1     Keyboard only
-10    2     Thinklight only
+# Haswell ThinkPads have no Thinklight
+#10    0     Both
+10    1     Keyboard
+#10    2     Thinklight only
 10    3     None
 #12    0     Integrated Only
 #12    1     Discrete Only

src/mainboard/lenovo/t440p/devicetree.cb

@@ -83,6 +83,7 @@ chip northbridge/intel/haswell
 					register "config1" = "0x0d"
 					register "config2" = "0xa8"
 					register "config3" = "0xc4"
+					register "has_keyboard_backlight" = "1"
 					register "event2_enable" = "0xff"
 					register "event3_enable" = "0xff"
 					register "event4_enable" = "0xd0"