Clean up STACKSIZE redefinition

kernel/power/dgemm_kernel_16x4_power8.S

@@ -82,12 +82,10 @@ USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #endif
 
 #ifdef __64BIT__
-#define STACKSIZE 320
 #define STACKSIZE 512
 #define ALPHA_SP   296+192(SP)
 #define FZERO	304+192(SP)
 #else
-#define STACKSIZE 240
 #define STACKSIZE 440
 #define ALPHA_SP   224+200(SP)
 #define FZERO	232+200(SP)