fbdev: move logo externs to header file

Now we have __initconst, we can finally move the external declarations for
the various Linux logo structures to <linux/linux_logo.h>.

James' ack dates back to the previous submission (way to long ago), when the
logos were still __initdata, which caused failures on some platforms with some
toolchain versions.

Signed-off-by: Geert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
Acked-by: James Simmons <jsimmons@infradead.org>
Cc: Krzysztof Helt <krzysztof.h1@poczta.fm>
Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>