[helloworld] Replaced printk() by pr_alert()

Replaced printk by pr_* wrapper macros.

Change-Id: I17bcd915dad3e68f24081026627c3ef5c7f83ce2
[one] Fixed code formatting and style issue

    Replaced printk by pr_* wrapper macros and formatting issues

Change-Id: Ib9bb53e3db535656121c7ec8ef370831dcf39b05
[intn] Fixed code formatting and style issue

    Replaced printk by pr_* wrapper macros and formatting issues

Change-Id: I899d6cae5c476ea84217db33d692d2c9b139676f