net: axienet: Replace the occurrences of (1<<x) by BIT(x)

Replace all occurences of (1<<x) by BIT(x) to get rid of checkpatch.pl
"CHECK" output "Prefer using the BIT macro".

Signed-off-by: Appana Durga Kedareswara Rao <appana.durga.rao@xilinx.com>
Signed-off-by: Radhey Shyam Pandey <radhey.shyam.pandey@amd.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>