Documentation: misc-devices: Rename freefall.c from hpfall.c in lis2lv02d

hpfall.c was renamed to freefall.c in 3.16, but this file still refer to
hpfall.c instead of freefall.c
Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/misc-devices/lis3lv02d

@@ -59,7 +59,7 @@ acts similar to /dev/rtc and reacts on free-fall interrupts received
 from the device. It supports blocking operations, poll/select and
 fasync operation modes. You must read 1 bytes from the device.  The
 result is number of free-fall interrupts since the last successful
-read (or 255 if number of interrupts would not fit). See the hpfall.c
+read (or 255 if number of interrupts would not fit). See the freefall.c
 file for an example on using the device.