Remove warning: unused variable 'volatile_var' [-Wunused-variable]

This occured in gcc-6.2.1.

The variable wasn't used so was no need to be volatile either.
Signed-off-by: Daniel Black <daniel.black@au.ibm.com>

storage/innobase/include/ut0ut.h

@@ -90,9 +90,7 @@ struct ut_when_dtor {
 #  define UT_RELAX_CPU() YieldProcessor()
 # elif defined(__powerpc__)
 #include <sys/platform/ppc.h>
-#  define UT_RELAX_CPU() do { \
-     volatile lint      volatile_var = __ppc_get_timebase(); \
-   } while (0)
+#  define UT_RELAX_CPU() __ppc_get_timebase()
 # else
 #  define UT_RELAX_CPU() ((void)0) /* avoid warning for an empty statement */
 # endif

storage/xtradb/include/ut0ut.h

@@ -87,9 +87,7 @@ struct ut_when_dtor {
 #  define UT_RELAX_CPU() YieldProcessor()
 # elif defined(__powerpc__)
 #include <sys/platform/ppc.h>
-#  define UT_RELAX_CPU() do { \
-     volatile lint      volatile_var = __ppc_get_timebase(); \
-   } while (0)
+#  define UT_RELAX_CPU() __ppc_get_timebase()
 # else
 #  define UT_RELAX_CPU() ((void)0) /* avoid warning for an empty statement */
 # endif