fbcon: Fix incorrect printed function name in fbcon_prepare_logo()

If the boot logo does not fit, a message is printed, including a wrong
function name prefix.  Instead of correcting the function name (or using
__func__), just use "fbcon", like is done in several other messages.

While at it, modernize the call by switching to pr_info().

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Helge Deller <deller@gmx.de>