regulator: da9063: fix null pointer deref with partial DT config

In the Linux kernel, the following vulnerability has been resolved: regulator: da9063: fix null pointer deref with partial DT config When some of the da9063 regulators do not have corresponding DT nodes a null pointer dereference occurs on boot because such regulators have no init_data causing the pointers calculated in da9063_check_xvp_constraints() to be invalid. Do not dereference them in this case.