SMC911x driver fixed for NFS boot

SMC911x driver fixed for NFS boot

eth_halt() function in the smc911x drivers used to call the
smc911x_reset() function. eth_halt() used to be called after
tftp transfers. This used to put the ethernet chip in reset
while the linux boots up resulting in the ethernet driver
not coming up. NFS boot used to fail as a result.

This patch calls smc911x_shutdown() instead of smc911x_reset().
Some comments received has also been fixed.

Signed-off-by: Manikandan Pillai <mani.pillai@ti.com>
Signed-off-by: Ben Warren <biggerbadderben@gmail.com>