Correct spec_idx in bta_dm_pm_cfg

After adding separate sniff mode settings for gamepads,
all the spec_idxes in bta_dm_pm_cfg larger than 6 are
not shifted by 1.
Correct the spec_idx to use the right bta_dm_pm_spec.

Fixes: 134444864
Test: Send data through OPP, data should be large enough
      to send over 30s.
      Before this fix, when we send data through OPP,
      it will enter sniff mode after 30s because of
      using the wrong spec_idx.
      After this fix, it will not enter sniff mode.

Change-Id: I9dcd3e8b075b35fa09a08e32cc8ff1522b8cd6ca