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.