[Kobo] Unbreak the FL ramp-up/down (#5421)

I got my wires crossed.

It's fast on Mk. 5, slow on Mk. 7.
So, slow it down on Mk. 5 so we actually get a ramp and not a jump.

frontend/device/kobo/powerd.lua

@@ -321,8 +321,9 @@ function KoboPowerD:turnOffFrontlightHW()
     util.runInSubProcess(function()
         for i = 1,5 do
             self:_setIntensity(math.floor(self.fl_intensity - ((self.fl_intensity / 5) * i)))
-            -- NOTE: We generally don't need to sleep when using sysfs as a backend...
-            if self.device:hasNaturalLight() and not self.device:hasNaturalLightMixer() then
+            --- @note: Newer devices appear to block slightly longer on FL ioctls/sysfs, so only sleep on older devices,
+            ---        otherwise we get a jump and not a ramp ;).
+            if not self.device:hasNaturalLight() then
                 if (i < 5) then
                     util.usleep(35 * 1000)
                 end
@@ -359,7 +360,9 @@ function KoboPowerD:turnOnFrontlightHW()
     util.runInSubProcess(function()
         for i = 1,5 do
             self:_setIntensity(math.ceil(self.fl_min + ((self.fl_intensity / 5) * i)))
-            if self.device:hasNaturalLight() and not self.device:hasNaturalLightMixer() then
+            --- @note: Newer devices appear to block slightly longer on FL ioctls/sysfs, so only sleep on older devices,
+            ---        otherwise we get a jump and not a ramp ;).
+            if not self.device:hasNaturalLight() then
                 if (i < 5) then
                     util.usleep(35 * 1000)
                 end