max17042_battery: Divide by 0 crash because r_sns init too late

On MMP2 brownstone divide by 0 error since probe sets r_sns
after calling power_supply_register.

Move the code up a few lines.  r_sns comes from the platform
data.

PROP_CURRENT_AVG and PROP_CURRENT divide the result by r_sns.

Signed-off-by: Philip Rakity <prakity@marvell.com>
Acked-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>