lp8727_charger: Clean up lp8727 definitions

All definitions should be unique, since they're in the gloabl namespace.
So the prefix LP8727_ are added. Additionally, use BIT() macro for bit
masks. Remove unnecessary definitions such as SW_DM1_U1 and SW_DP2_U2.

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