lib: do not provide hexdump in SPL

SPL should not be enlarged by building with CONFIG_HEXDUMP=y.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/lib/hexdump.c b/lib/hexdump.c
index bf14b5b..a3f219a 100644
--- a/lib/hexdump.c
+++ b/lib/hexdump.c
@@ -18,7 +18,7 @@
 const char hex_asc[] = "0123456789abcdef";
 const char hex_asc_upper[] = "0123456789ABCDEF";
 
-#ifdef CONFIG_HEXDUMP
+#if CONFIG_IS_ENABLED(HEXDUMP)
 /**
  * hex_dump_to_buffer - convert a blob of data to "hex ASCII" in memory
  * @buf: data blob to dump