HID: hid-lg4ff: Replace DEVICE_ATTR_RW with DEVICE_ATTR to have all internal function...

HID: hid-lg4ff: Replace DEVICE_ATTR_RW with DEVICE_ATTR to have all internal functions prefixed with "lg4ff_"

Replace DEVICE_ATTR_RW with DEVICE_ATTR to have all internal functions prefixed
with "lg4ff_". All internal functions should be prefixed with just "lg4ff_".
Usage of DEVICE_ATTR_RW breaks this scheme because it expects the functions'
names to match the name of the respective sysfs entry.
This partially reverts "2f1cec3250e38609bf9252db52dbbe61603c04a7"

Signed-off-by: Michal Malý <madcatxster@devoid-pointer.net>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>