dt-bindings: batterydata: Add qcom,batt-age-level property

Add qcom,batt-age-level property for battery profile device which
if specified would indicate the battery age level for that
battery profile.

Change-Id: I2c9fd71f2bf2fb52e082c4dab3ca4c5db1302a2f
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>