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/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index b481db1..28fdf4f 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -1217,7 +1217,6 @@
 {
 	unsigned long size, offset;
 	const char *name;
-	char *modname;
 
 	*startp = *endp = 0;
 	if (pc == 0)
@@ -1225,7 +1224,7 @@
 	if (setjmp(bus_error_jmp) == 0) {
 		catch_memory_errors = 1;
 		sync();
-		name = kallsyms_lookup(pc, &size, &offset, &modname, tmpstr);
+		name = kallsyms_lookup(pc, &size, &offset, NULL, tmpstr);
 		if (name != NULL) {
 			*startp = pc - offset;
 			*endp = pc - offset + size;