power: smb1351-charger: Check if SMB1351 is present before configuring it

While configuring SMB1351 for parallel operation do a dummy read of
the SMB1351 version register to check if it is present.

Change-Id: Ib5f5646a40f8f595238ffb8f79a2b27b468cfc8d
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>