drm/amdkfd: Use dynamic allocation for CU occupancy array in 'kfd_get_cu_occupancy()'

In the Linux kernel, the following vulnerability has been resolved:

drm/amdkfd: Use dynamic allocation for CU occupancy array in 'kfd_get_cu_occupancy()'

The `kfd_get_cu_occupancy` function previously declared a large
`cu_occupancy` array as a local variable, which could lead to stack
overflows due to excessive stack usage. This commit replaces the static
array allocation with dynamic memory allocation using `kcalloc`,
thereby reducing the stack size.

This change avoids the risk of stack overflows in kernel space, in
scenarios where `AMDGPU_MAX_QUEUES` is large. The allocated memory is
freed using `kfree` before the function returns to prevent memory
leaks.

Fixes the below with gcc W=1:
drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_process.c: In function ‘kfd_get_cu_occupancy’:
drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_process.c:322:1: warning: the frame size of 1056 bytes is larger than 1024 bytes [-Wframe-larger-than=]
322 | }
| ^