Cervantes: Make sure the warmth scaling is accurate

For some mysterious reason, we init fl_warmth_max to 100 on Kobo &
Cervantes, despite this being the case on absolutely none of them.

TL;DR: We update it according to nl_max during init, but this was
missing on Cervantes.

frontend/device/cervantes/powerd.lua

@@ -51,10 +51,13 @@ function CervantesPowerD:init()
         if self.device:hasNaturalLight() then
             local nl_config = G_reader_settings:readSetting("natural_light_config")
             if nl_config then
-                for key,val in pairs(nl_config) do
+                for key, val in pairs(nl_config) do
                     self.device.frontlight_settings[key] = val
                 end
             end
+            -- Does this device's NaturalLight use a custom scale?
+            self.fl_warmth_min = self.device.frontlight_settings.nl_min or self.fl_warmth_min
+            self.fl_warmth_max = self.device.frontlight_settings.nl_max or self.fl_warmth_max
             -- If this device has a mixer, we can use the ioctl for brightness control, as it's much lower latency.
             if self.device:hasNaturalLightMixer() then
                 local kobolight = require("ffi/kobolight")

frontend/device/kobo/powerd.lua

@@ -139,8 +139,7 @@ function KoboPowerD:init()
         --- @note: Newer devices appear to block slightly longer on FL ioctls/sysfs, so we only really need a delay on older devices.
         self.device.frontlight_settings.ramp_delay = self.device.frontlight_settings.ramp_delay or (self.device:hasNaturalLight() and 0.0 or 0.025)
 
-        -- If this device has natural light (currently only KA1 & Forma)
-        -- Use the SysFS interface, and ioctl otherwise.
+        -- If this device has natural light, use the sysfs interface, and ioctl otherwise.
         -- NOTE: On the Forma, nickel still appears to prefer using ntx_io to handle the FL,
         --       but it does use sysfs for the NL...
         if self.device:hasNaturalLight() then