Define all the `ETH_P_*` constants on fuchsia

[ghananigans]

Currently, libc only defines ETH_P_IP on Fuchsia. We should define all of the ETH_P_* constants that fuchsia supports per https://cs.opensource.google/fuchsia/fuchsia/+/main:zircon/third_party/ulib/musl/include/netinet/if_ether.h