igbvf: Convert printks to pr_<level>

Based on the previous patch from Joe Perches <joe@perches.com>

Use current logging styles.

Prefix all output via #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
Neaten link status dev_info.

-v2 Remove Copyright changes and fix-up patch to make it checkpatch.pl
    compliant.

CC: Joe Perches <joe@perches.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Tested-by: Sibai Li <sibai.li@intel.com>