stress-cachehammer: add missing const on pointer cast

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>

Author: ColinIanKing

stress-cachehammer.c

@@ -339,7 +339,7 @@ static void OPTIMIZE3 hammer_write64(
 			if (UNLIKELY(val != pattern)) {
 				pr_fail("%s: write64: read back of stored value at address "
 					"%p not %" PRIx64 ", got %" PRIx64 " instead\n",
-					args->name, (volatile void *)vptr, pattern, val);
+					args->name, (const volatile void *)vptr, pattern, val);
 			}
 		}
 	}
@@ -528,7 +528,7 @@ static void OPTIMIZE3 hammer_writeread64(
 			if (UNLIKELY(val != pattern)) {
 				pr_fail("%s: writeread64: read back of stored value at address "
 					"%p not %" PRIx64 ", got %" PRIx64 " instead\n",
-					args->name, (volatile void *)vptr, pattern, val);
+					args->name, (const volatile void *)vptr, pattern, val);
 			}
 		}
 	}