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.

Fixes: 3afb50d7 ("power: supply: core: Add some helpers to use the battery OCV capacity table")
Signed-off-by: ruanjinjie <ruanjinjie@huawei.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>