Simplify kallsyms_lookup()

Several kallsyms_lookup() pass dummy arguments but only need, say, module's
name.  Make kallsyms_lookup() accept NULLs where possible.

Also, makes picture clearer about what interfaces are needed for all symbol
resolving business.

Signed-off-by: Alexey Dobriyan <adobriyan@sw.ru>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/sh64/kernel/unwind.c b/arch/sh64/kernel/unwind.c
index f934f97..1214c78 100644
--- a/arch/sh64/kernel/unwind.c
+++ b/arch/sh64/kernel/unwind.c
@@ -46,15 +46,15 @@
 		      struct pt_regs *regs)
 {
 	const char *sym;
-	char *modname, namebuf[128];
-	unsigned long offset, size;
+	char namebuf[128];
+	unsigned long offset;
 	unsigned long prologue = 0;
 	unsigned long fp_displacement = 0;
 	unsigned long fp_prev = 0;
 	unsigned long offset_r14 = 0, offset_r18 = 0;
 	int i, found_prologue_end = 0;
 
-	sym = kallsyms_lookup(pc, &size, &offset, &modname, namebuf);
+	sym = kallsyms_lookup(pc, NULL, &offset, NULL, namebuf);
 	if (!sym)
 		return -EINVAL;