net: bpqether.h: remove if_ether.h guard

__LINUX_IF_ETHER_H is not defined anywhere, and if_ether.h can keep itself from
double inclusion, though it uses a single underscore prefix.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: David S. Miller <davem@davemloft.net>