lib: bridge: avoid redefinition of in6_addr

On musl libc, which does not use the kernel definitions of in6_addr, including
the libc headers after the kernel (UAPI) headers would cause a redefinition
error. The opposite order avoids the redefinition.

Fixes: 9e89d5b94d749f37525cd8778311e1c9f28f172a
Signed-off-by: Yureka <yureka@cyberchaos.dev>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>