power: qpnp-fg-gen4: Support profile loading based on battery age level

Add support for multiple profile loading based on battery age
level. User can select a profile based on batt_age_level property
runtime. If a valid profile exists for the battery age level, it
will be loaded. By default, a profile with age level 0 will be
loaded if the feature is enabled.

While at it, split the function fg_gen4_get_batt_profile() that
parse the parameters to reduce CCN warnings.

Change-Id: Ic52bf77a15f4aa16f6d3da058b0b26043879e3a1
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>