power: qpnp-linear-charger: Do not configure ADC_BTM for fake_battery

Skip registering for BTM on the BAT_THERM channel if
fake_battery config is enabled to avoid wakeup's from
the ADC_BTM.

Change-Id: I9ee7ecd72410d43f45682ca0e17632a61abfe721
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>