crx string overflow warning

gcc8 complains wrongly about the buffer not being large enough, at
least at -Og optimization.

	* crx-dis.c (getregliststring): Allocate a large enough buffer
	to silence false positive gcc8 warning.

opcodes/ChangeLog

@@ -1,3 +1,8 @@
+2018-02-26  Alan Modra  <amodra@gmail.com>
+
+	* crx-dis.c (getregliststring): Allocate a large enough buffer
+	to silence false positive gcc8 warning.
+
 2018-02-22  Shea Levy <shea@shealevy.com>
 
 	* disassemble.c (ARCH_riscv): Define if ARCH_all.

opcodes/crx-dis.c

@@ -244,7 +244,7 @@ powerof2 (int x)
 void
 getregliststring (int mask, char *string, enum REG_ARG_TYPE core_cop)
 {
-  char temp_string[5];
+  char temp_string[16];
   int i;
 
   string[0] = '{';