drm/amdkfd: Clear VRAM on allocation to prevent stale data exposure

In the Linux kernel, the following vulnerability has been resolved: drm/amdkfd: Clear VRAM on allocation to prevent stale data exposure KFD VRAM allocations set AMDGPU_GEM_CREATE_VRAM_WIPE_ON_RELEASE but not AMDGPU_GEM_CREATE_VRAM_CLEARED, leaving freshly allocated VRAM with stale data from prior use observable by compute kernels. The GEM ioctl path already sets VRAM_CLEARED for all userspace allocations via amdgpu_gem_create_ioctl() and amdgpu_mode_dumb_create(). The KFD path was missing this flag, allowing stale page table remnants to leak into user buffers. This causes crashes in RCCL P2P transport where non-zero data in ptrExchange/head/tail fields corrupts the protocol handshake.