qpnp-smb2: Fix QC_PULSE_COUNT reading logic

QC_PULSE_COUNT register offset differs between PMI8998 and
PM660. Use common function "smblib_get_pulse_cnt" to read
the pulse count instead of directly reading the register.
While at it, update the "smblib_get_pulse_cnt" function
to return software based pulse count if HW INOV is disabled.

Change-Id: Iab935b352dd75365d1f9862d7a7986cd1c476f66
Signed-off-by: Ashay Jaiswal <ashayj@codeaurora.org>