lp8727_charger: Use the definition rather than enum

Enum lp8727_chg_state can be removed because only one charger status is
used - EOC(End Of Charge).

To check whether the EOC is reached or not, use simple comparison rather
than shift-operation.

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