Fix wrong type on aarch64

[ed10vi]

Trying to build in a Raspberry Pi I get the following error:

error[E0308]: mismatched types
    --> /root/whisper-rs/src/vulkan.rs:33:69
     |
33   |                 ggml_backend_vk_get_device_description(id as c_int, tmp.as_mut_ptr(), tmp.len());
     |                 --------------------------------------              ^^^^^^^^^^^^^^^^ expected `*mut u8`, found `*mut i8`
     |                 |
     |                 arguments to this function are incorrect
     |
     = note: expected raw pointer `*mut u8`
                found raw pointer `*mut i8`
note: function defined here
    --> /root/whisper-tst/target/debug/build/whisper-rs-sys-fdc42e82b8d8a876/out/bindings.rs:5345:12
     |
5345 |     pub fn ggml_backend_vk_get_device_description(
     |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error[E0308]: mismatched types
  --> /root/whisper-rs/src/vulkan.rs:39:42
   |
39 |                     name: CStr::from_ptr(tmp.as_ptr()).to_string_lossy().into_owned(),
   |                           -------------- ^^^^^^^^^^^^ expected `*const u8`, found `*const i8`
   |                           |
   |                           arguments to this function are incorrect
   |
   = note: expected raw pointer `*const u8`
              found raw pointer `*const i8`

See: remacs/remacs#1393