1. Fix error recovery mechanism during transmission error
handling (enable transmission at the end).
2. Fix compilation / operation with CONFIG_SAMV7_EMAC_PREALLOCATE=y
3. Enable fully configured address space for transmission queues
to allow sending packets with length more than 976 bytes. With
partially configured address space the AHB error is generated
during transmission of long packets.
Signed-off-by: Petro Karashchenko <petro.karashchenko@gmail.com>