Add support for `a15x`

### Is your device already requested?

- [x] I have searched the existing issues

### Brand

Samsung

### Name

Galaxy A15 5G 

### Device code

SM-A156M

### Model

SM-A156M

### Device images

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### Do you own the device and would be willing to test the installer?

- [x] I own the device and am willing to test the installer on it.

### Additional context

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