Fix Bluetooth crash when pairing with 8th HOGP device

In function bta_hh_hdl_event, when handling with
the event of BTA_HH_API_GET_DSCP_EVT after bonded
with 8th HOGP device, no correct p_cb will be found,
due to mapping error between the device handle and
dev cb for HOGP. Then NPE happen.
Change to map le_cb_index into the device handle for
HOGP, so that HOGP and HID can be separately maintained
maximum to 14 device

Test: Pair with 14 HOGP devices
Change-Id: I8556f1ffea160862c2e52f874ef334f68c17050e