musa: handle __hgt2_mask (available starting from MUSA SDK rc4.3.0)

[yeahdongcn]

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__hgt2_mask will be available starting from MUSA SDK rc4.3.0.

The following code snippet shows how MUSART_VERSION is calculated:

#define __MUSA_API_VER_MAJOR__      4
#define __MUSA_API_VER_MINOR__      2
#define __MUSA_API_VER_PATCH__      0
#define __MUSA_API_VER_TWEAK__      
#define __MUSART_API_VERSION ((__MUSA_API_VER_MAJOR__ * 10000) + (__MUSA_API_VER_MINOR__ * 100) + __MUSA_API_VER_PATCH__)
#define MUSART_VERSION              __MUSART_API_VERSION

Testing Done

Extra build test on HIP with -DGGML_HIP_ROCWMMA_FATTN=ON passed:

HIPCXX="$(hipconfig -l)/clang" HIP_PATH="$(hipconfig -R)" \
    cmake -S . -B build -DGGML_HIP=ON -DGGML_HIP_ROCWMMA_FATTN=ON -DCMAKE_BUILD_TYPE=Release \
    && cmake --build build --config Release -- -j $(nproc)