power: qpnp-fg-gen4: Fix a possible NULL pointer dereference

Currently, in get_batt_psy_props(), batt_psy can be used even
before it can be obtained. Fix it.

CRs-Fixed: 2221940
Change-Id: Icc86695f89a53802d60a6e2c4dd97b58922d267f
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>