power: supply: fix null pointer dereferencing in power_supply_get_battery_info

In the Linux kernel, the following vulnerability has been resolved: power: supply: fix null pointer dereferencing in power_supply_get_battery_info when kmalloc() fail to allocate memory in kasprintf(), propname will be NULL, strcmp() called by of_get_property() will cause null pointer dereference. So return ENOMEM if kasprintf() return NULL pointer.