net: Use lighter printk() instead of printf()

Use printk(), snprintk() instead of printf() and snprintf().
CONFIG_STDOUT_CONSOLE is anyway disabled by default so printf()
will not output anything without it.

Change-Id: I9ad778e318fe999e79ec34182f2de8574e45b7d4
Signed-off-by: Ravi kumar Veeramally <ravikumar.veeramally@linux.intel.com>