drm/amdkfd: Hardware DWORD size is 4 bytes

Don't use sizeof(uint32_t) or similar types for hardware or firmware
DWORD size. The hardware and firmware don't care about Linux types.

Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>