staging/et131x: fix checkpatch warnings

The below checkpatch warns was fixed,

drivers/staging/et131x/et131x.c:2556: WARNING: Prefer pr_info(... to printk(KERN_INFO, ...
drivers/staging/et131x/et131x.c:2577: WARNING: Prefer pr_info(... to printk(KERN_INFO, ...
drivers/staging/et131x/et131x.c:5189: WARNING: Prefer pr_info(... to printk(KERN_INFO, ...

And fixed below,
-added pr_fmt
-fixed printk formats for dma_addr_t
-converted printk to netdev_info

Signed-off-by: Toshiaki Yamane <yamanetoshi@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>