mfd: palmas: is_palmas_charger needed by multiple drivers

is_palmas_charger checks for the presence of charging
functionality in the device

Signed-off-by: Graeme Gregory <gg@slimlogic.co.uk>
Signed-off-by: Ian Lartey <ian@slimlogic.co.uk>
Acked-by: Laxman Dewangani <ldewangan@nvidia.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>