Avoid memcpy_s() in putinthex

- Use a define for size of buffer.
- Avoid using memcpy_s() or memcpy_s(). Just set directly in the
  buffer.

libcommon/io.c

@@ -261,23 +261,26 @@ void puthex(enum ioend dest, const uint8_t c)
 	write(dest, hexbuf, 2);
 }
 
+// Size of of a maximum integer in hex text format
+#define INTBUFSIZE 10
+
 void putinthex(enum ioend dest, const uint32_t n)
 {
-	uint8_t buf[10];
-	uint8_t hexbuf[2];
+	uint8_t buf[INTBUFSIZE] = {0};
+	uint8_t hexbuf[2] = {0};
 	uint8_t *intbuf = (uint8_t *)&n;
+	int j = 0;
 
-	buf[0] = '0';
-	buf[1] = 'x';
+	buf[j++] = '0';
+	buf[j++] = 'x';
 
-	int j = 2;
 	for (int i = 3; i > -1; i--) {
 		hex(hexbuf, intbuf[i]);
-		memcpy_s(&buf[j], 10 - j, hexbuf, 2);
-		j += 2;
+		buf[j++] = hexbuf[0];
+		buf[j++] = hexbuf[1];
 	}
 
-	write(dest, buf, 10);
+	write(dest, buf, INTBUFSIZE);
 }
 
 void puts(enum ioend dest, const char *s)