[POWERPC] Fix for via-pmu based backlight control

This fixes a few issues with via-pmu based backlight control.

First, it fixes a sign problem with the setup of the backlight
curve since the `range' value there -can- (and will) go negative.

Then, it reworks the interaction between this and the via-pmu sleep
code to properly restore backlight on wakeup from sleep.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/include/linux/pmu.h b/include/linux/pmu.h
index 177ae48..4c5f653 100644
--- a/include/linux/pmu.h
+++ b/include/linux/pmu.h
@@ -159,6 +159,8 @@
 extern int pmu_present(void);
 extern int pmu_get_model(void);
 
+extern void pmu_backlight_set_sleep(int sleep);
+
 #define PMU_MAX_BATTERIES	2
 
 /* values for pmu_power_flags */