amdgpu: Adjust kmalloc_array calls for new -Walloc-size

GCC 14 introduces a new -Walloc-size included in -Wextra which errors out
on various files in drivers/gpu/drm/amd/amdgpu like:
```
amdgpu_amdkfd_gfx_v8.c:241:15: error: allocation of insufficient size ‘4’ for type ‘uint32_t[2]’ {aka ‘unsigned int[2]'} with size ‘8’ [-Werror=alloc-size]
```

This is because each HQD_N_REGS is actually a uint32_t[2]. Move the * 2 to
the size argument so GCC sees we're allocating enough.

Originally did 'sizeof(uint32_t) * 2' for the size but a friend suggested
'sizeof(**dump)' better communicates the intent.

Link: https://lore.kernel.org/all/87wmuwo7i3.fsf@gentoo.org/


Signed-off-by: Sam James <sam@gentoo.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>