ixgbevf: Convert printks to pr_<level>

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

Use the current logging styles, prefix output with "ixgbevf: "

Add #define pr_fmt
Coalesce formats.

-v2 Fix-up to make checkpatch.pl compliant and remove change to
    copyright line

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