i.mx6:imx6q: allign MAC address with burned-in ordering

For the i.mx6q, the burned-in MAC address will be the following odering,

fuse: 0x620[7:0]   MAC_ADDR[7:0]     ---> mac[5]
fuse: 0x620[15:8]  MAC_ADDR[15:8]    ---> mac[4]
fuse: 0x620[23:16] MAC_ADDR[23:16]   ---> mac[3]
fuse: 0x620[31:24] MAC_ADDR[31:24]   ---> mac[2]
fuse: 0x630[7:0]   MAC_ADDR[39:32]   ---> mac[1]
fuse: 0x630[15:8]  MAC_ADDR[47:40]   ---> mac[0]

This patch also fix the error caculation for the fuse bank[0] address

Signed-off-by: Jason Liu <jason.hui@linaro.org>
Cc: Stefano Babic <sbabic@denx.de>