m68k: arch/m68k/kernel/sun3-head.S needs <linux/init.h>

Fix this:

arch/m68k/kernel/sun3-head.S: Assembler messages:
arch/m68k/kernel/sun3-head.S:32: Error: Unknown operator -- statement `__head' ignored

Introduced by commit 6f335cab0431d5df4995bcd4fd952d4c746d5a86 ("m68k:
convert to use __HEAD and HEAD_TEXT macros."), which started using
__HEAD without adding the appropriate include.

Signed-off-by: Geert Uytterhoeven <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/m68k/kernel/sun3-head.S

···
 #include <linux/linkage.h>
+#include <linux/init.h>
 
 #include <asm/entry.h>
 #include <asm/page.h>