module: Fix pr_fmt() bug for header use of printk

This commit removes the pr_fmt() macro, replacing it with mod_err() and
mod_debug() macros to avoid errors when using printk() from header files.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>