net: emaclite: Fix logic around available TX buffers

Simplify logic how to find out if there is free TX buffer.
Both buffers are checked all the time that's why logic around order
can be removed.
Also add check when only one buffer is available.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
1 file changed