power: supply: qti-battery-charger: Fix buffer handling in handle_message()

Currently, prop_id (u32) and val (u32) are obtained for all messages
in handle_message(). However, the response for notification request
doesn't have the same payload but only an u32 return code. Because
of this, an unintentional memory read for u32 is being made even
though it is not used.

Fix this by getting prop_id and val only for response messages that
are intended to get battery/USB/wireless power supply properties.

CRs-Fixed: 2655408
Change-Id: I4d17d965f911eb6a4357e29117191f78830e9e5c
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>