power: smb1351-charger: add support for reading charger version

Add support to read the charger version whether it is SMB1350 or
SMB1351. This is needed to set different parameters based on the
chip version.

Change-Id: Ifc3569bc9973ca38081ecbdb7ab0cba52faa261e
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>