device: Update Z_DEVICE_INIT_ENTRY_DEFINE to be C++ compatible

The `Z_DEVICE_INIT_ENTRY_DEFINE()` macro uses a designated initializer
to define a struct. Ensure all members of `struct init_entry` are
defined in order for C++ compatibility.

Signed-off-by: Tristan Honscheid <honscheid@google.com>
1 file changed