softrvv: fix incompatible type

Change-Id: I9982740341a243b11252a39959fcd03dcb3d666f

softrvv/include/softrvv_vadd.h

diff --git a/softrvv/include/softrvv_vadd.h b/softrvv/include/softrvv_vadd.h
index 96271a7..ae712c6 100644
--- a/softrvv/include/softrvv_vadd.h
+++ b/softrvv/include/softrvv_vadd.h
@@ -8,25 +8,25 @@
 
 template <typename T>
 void vadd_vi(T *dest, T *src1, T src2, size_t avl) {
-  for (int idx = 0; idx < avl; idx++) {
+  for (size_t idx = 0; idx < avl; idx++) {
     dest[idx] = src1[idx] + src2;
   }
 }
 
 template <typename T>
 void vadd_vx(T *dest, T *src1, const T *src2, size_t avl) {
-  for (int idx = 0; idx < avl; idx++) {
+  for (size_t idx = 0; idx < avl; idx++) {
     dest[idx] = src1[idx] + *src2;
   }
 }
 
 template <typename T>
 void vadd_vv(T *dest, T *src1, T *src2, size_t avl) {
-  for (int idx = 0; idx < avl; idx++) {
+  for (size_t idx = 0; idx < avl; idx++) {
     dest[idx] = src1[idx] + src2[idx];
   }
 }
 
 }  // namespace softrvv
 
-#endif  // SOFTRVV_VADD_H
\ No newline at end of file
+#endif  // SOFTRVV_VADD_H