PMU battery: filenames in sysfs with spaces

By changing drivers/power/pmu_battery.c I now have '_' instead of
' ' (spaces) in /sys:

/sys/devices/platform/pmu-battery.0/power_supply/PMU_battery_0
/sys/class/power_supply/PMU_battery_0

I'm still not sure if some userspace tool out there uses the old paths and
will break now.

Signed-off-by: Christian Kujau <lists@nerdbynature.de>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>