ethdev: rename folder to library name

ethdev: rename folder to library name

Library folder name and output library name are same except a few flaws
including librte_ether.

This library is network device abstraction layer, the name "ethdev" fits
better than "ether", and library & header files already named as ethdev.

Also there is a rte_ether.h in the net library which can cause confusion.

Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>