power: supply: charger-manager: drop unused charger assignment

The 'charger' variable in error path is assigned but never used:

  drivers/power/supply/charger-manager.c: In function 'charger_manager_probe':
  drivers/power/supply/charger-manager.c:1626:29: warning: variable 'charger' set but not used [-Wunused-but-set-variable]

Fixes: c1f73028 ("power: supply: charger-manager: Update extcon functions")
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>