mb/purism/librem_mini: Adjust PL1/2 levels

While the Librem Mini (v1/v2) are more than capable of higher
PL1/2, they currently ship with a 40W power supply, so set PL1/2
accordingly to avoid power spikes above the PSU rating (which can
result in unexpected showdowns/reboots)

Change-Id: Ia7f89e885f1af29cbbb67d6fb844257ba2b87417
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/48586
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

src/mainboard/purism/librem_cnl/variants/librem_mini/devicetree.cb

@@ -7,8 +7,8 @@ chip soc/intel/cannonlake
 # CPU (soc/intel/cannonlake/cpu.c)
 	# Power limit
 	register "power_limits_config" = "{
-		.tdp_pl1_override = 25,
-		.tdp_pl2_override = 51,
+		.tdp_pl1_override = 15,
+		.tdp_pl2_override = 28,
 	}"
 
 	# Enable Enhanced Intel SpeedStep