Fix OpenCL compilation on newer AMD drivers

[dimaniojk]

## Summary

Fixes OpenCL kernel compilation on newer AMD ROCm/OpenCL compilers,
including RDNA 4 `gfx1200`.

## Problem

The kernel passes pointers to entire arrays:

```c
sha512_hash(&key, &hash);

Newer AMD OpenCL compilers reject this because the function expects
pointers to uchar, not pointers to array types.

The build fails with errors similar to:

error: incompatible pointer types passing '__private uchar (*)[32]'
to parameter of type 'const __private uchar *'

error: incompatible pointer types passing '__private uchar (*)[64]'
to parameter of type '__private uchar *'

Fix

Pass the arrays directly:

sha512_hash(key, hash);

Arrays decay to the required element pointers when passed to the function.

Tested on

• NixOS
• AMD ROCm OpenCL
• AMD RDNA 4 / gfx1200
• Rust release build
• Approximately 15.5–15.8 MH/s

After this change, the OpenCL kernel compiles and runs successfully.

A generated private key was also verified with Yggdrasil 0.5.13 and
reproduced the expected vanity IPv6 address.