ENGR00235090 FEC: Workaround for FEC RX hang with stress test

ENGR00235090 FEC: Workaround for FEC RX hang with stress test

When do Ethernet UDP stress overnight test with abundance of
data transmission, RX path may hang-on.
Dump the RX BD, found all BD "Empty" bit is cleared, which means
CPU read BD status is not right and waiting here.

Change BD memroy attribute from Normal to strongly ordered:
changes the memory attribute of C=0, B=0 instead of C=0, B=1.
Apply the change, the issue cannot be reproduced.

Signed-off-by: Fugang Duan  <B38611@freescale.com>