CMSIS-DSP: Removed compilation warning.

CMSIS/DSP/Source/TransformFunctions/arm_rfft_fast_f32.c

@@ -392,7 +392,7 @@ void stage_rfft_f32(
       pA += 2;
       pB -= 2;
       k--;
-   } while (k > 0U);
+   } while (k > 0);
 }
 
 /* Prepares data for inverse cfft */
@@ -422,7 +422,7 @@ void merge_rfft_f32(
    pB  =  p + 2*k ;
    pA +=  2	   ;
 
-   while (k > 0U)
+   while (k > 0)
    {
       /* G is half of the frequency complex spectrum */
       //for k = 2:N