max77759_charger: current_now return 0 when charger mode is invalid

*_PROP_CURRENT_NOW can be read from MW only when the charger is in mode
5, 6, 7, 0xe and 0xf.

Bug: 183038958
Test: check CURRENT_NOW on WLC, CHG and  OFF
Signed-off-by: AleX Pelosi <[email protected]>
Change-Id: Ieee5a08cb034d94fc0686cb15eedc0b1f01ecfcf
1 file changed