power: smb358-charger: Fix an uninitialized variable issue

Uninitialized cfg structure may cause random crash when calling
regulator_register() function. Fix this by initializing it to 0
by default.

While at it, fix another minor typo issue.

Change-Id: I0b96fd8f47091adacf1d3cd5d159509060a1a516
Signed-off-by: Zhenhua Huang <zhenhuah@codeaurora.org>