power: qpnp-fg: fix error condition in get_batt_id

The bias current is identified only by the lower two bits, and its
value can be 1, 2, or 3. The current bounds check is incorrect. Fix
it.

CRs-Fixed: 857879
Change-Id: Icf34d1144904b9d41f5181625dcf598c247e33d3
Signed-off-by: Nicholas Troast <ntroast@codeaurora.org>