[BUG] AMDGPU internal display brightness reduced on Linux 7.2 with Ryzen 7 5700U on Lenovo IdeaPad 5 14ALC05

### Pre-flight checklist

- [x] I have searched existing issues and this is not a duplicate.
- [x] I have read the [Contributing Guidelines](https://github.com/CachyOS/linux-cachyos/blob/master/CONTRIBUTING.md).
- [x] I have verified the issue is reproducible with the latest available CachyOS kernel.
- [x] I have tried to reproduce the issue on Arch Linux's `linux` kernel.

### Upstream / vanilla kernel check

I have not tested with a vanilla/upstream kernel

### Kernel variant

linux-cachyos (EEVDF, Clang)

### System information (cachyos-bugreport.sh)

```text
Kernel version : Linux 7.2.2-1-cachyos
CPU: AMD Ryzen 7 5700U
GPU: AMD Lucienne [Integrated]
Architecture: x86-64-v3
```

### Manual system information (if cachyos-bugreport.sh is unavailable)

```text

```

### Bug description

After upgrading from a working kernel to Linux 7.2.0-1-cachyos, the internal eDP display on my Ryzen 7 5700U laptop became significantly dimmer at the same brightness levels.

The backlight is exposed as amdgpu_bl1 with a maximum value of 65535. The AMDGPU backlight mapping differs substantially between the working kernel and 7.2:

Working kernel(<7.2):
```

0 -> 0

16384 -> 11051

32768 -> 27242

49152 -> 43690

65535 -> 58339
```

Linux 7.2:

```
0 -> 0

16384 -> 1670

32768 -> 5705

49152 -> 15959

65535 -> 42096
```

The physical display is noticeably dimmer on 7.2. The issue is reproducible and disappears when booting the previous working kernel.

amdgpu.dcdebugmask=0x40000 was also tested. It disables the "Using custom brightness curve" message, but does not resolve the brightness regression.

### Steps to reproduce

1. Boot into the kernel.
2. Notice that the display is noticeably dimmer.

### Expected behavior

The display should have been the same brightness as in the previous kernel versions.

### Actual behavior

The display is dimmer in kernel 7.2.

### Logs / stack traces

```text

```

### Additional system information

_No response_