ac/debug: use util_strchrnul() to fix android build error

Similar to e09d04cd56 "radeonsi: use util_strchrnul() to fix android build error"

Android Bionic does not support strchrnul() string function,
gallium auxiliary util/u_string.h provides util_strchrnul()

This change avoids the following warning and error:

external/mesa/src/amd/common/ac_debug.c:501:15: warning: implicit declaration of function 'strchrnul' is invalid in C99
                char *end = strchrnul(out, '\n');
                            ^
external/mesa/src/amd/common/ac_debug.c:501:9: error: incompatible integer to pointer conversion initializing 'char *' with an expression of type 'int'
                char *end = strchrnul(out, '\n');
                      ^     ~~~~~~~~~~~~~~~~~~~~
1 warning and 1 error generated.

Fixes: c2c3912410 "ac/debug: annotate IB dumps with the raw values"
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Signed-off-by: Rob Herring <robh@kernel.org>
diff --git a/src/amd/common/ac_debug.c b/src/amd/common/ac_debug.c
index 2af83a1..3daa556 100644
--- a/src/amd/common/ac_debug.c
+++ b/src/amd/common/ac_debug.c
@@ -39,6 +39,7 @@
 #include "sid_tables.h"
 #include "util/u_math.h"
 #include "util/u_memory.h"
+#include "util/u_string.h"
 
 /* Parsed IBs are difficult to read without colors. Use "less -R file" to
  * read them, or use "aha -b -f file" to convert them to html.
@@ -498,7 +499,7 @@
 		if (indent)
 			print_spaces(f, indent);
 
-		char *end = strchrnul(out, '\n');
+		char *end = util_strchrnul(out, '\n');
 		fwrite(out, end - out, 1, f);
 		fputc('\n', f); /* always end with a new line */
 		if (!*end)