power: qpnp-smbcharger: fix battery charging logic for battery types

Currently, the battery charging enable/disable logic for unknown and
loading batteries is incorrect. The current implementation will always
charge loading batteries and never charge if qcom,charge-unknown-battery
is defined.

Fix this by correcting the conditional check in check_battery_type.

CRs-Fixed: 861687
Change-Id: I427816a33b2bc44a573f03edc81045bfcc28e41f
Signed-off-by: Xiaozhe Shi <xiaozhes@codeaurora.org>