Mismatched include guard names

## Expected Behavior
The lines at: https://github.com/Azure/iot-hub-device-update/blob/develop/src/diagnostics_component/diagnostics_devicename/inc/diagnostics_devicename.h#L9

to have the same #ifndef as the #define:

```c
#ifndef DIAGNOSTICS_DEVICENAMES_H
# define DIAGNOSTICS_DEVICENAMES_H
```

## Current Behavior
Tell us what happens instead of the expected behavior

The lines ar now mismatched

```c
#ifndef DIAGNOSTICS_DEVICENAMES_H
# define DIAGNOSTICS_DEVICENAMES_UTILS_H
```

### Device Information
* Host OS Linux (Custom Yocto Installation)
* Architecture arm64

Open src/diagnostics_component/diagnostics_devicename/inc/diagnostics_devicename.h at the referenced lines and compare the #ifndef and #define names. Done means both guards use DIAGNOSTICS_DEVICENAMES_H consistently.

Written by the indexing model from the issue text.