tools: remove redundant ethtool.h from tooling infra

Remove the redundant ethtool.h header file from tools/include/uapi/linux.
The file is unnecessary as the system uses the kernel's
include/uapi/linux/ethtool.h directly.
Signed-off-by: Tushar Vyavahare <tushar.vyavahare@intel.com>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/r/20240508104123.434769-1-tushar.vyavahare@intel.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>