tools: include: Add ethtool_drvinfo definition to UAPI header

Instead of copying the whole header in, just add the struct definitions
we need for now. In the future it can be synced as a copy of in-tree
header if required.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210821002010.845777-3-memxor@gmail.com