lp8727_charger: Move header file into platform_data directory

The lp8727 header can be used only in the platform side, so it can be
moved to the platform_data directory.

Signed-off-by: Milo(Woogyom) Kim <milo.kim@ti.com>
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>