Use memmove to resolve memcpy-param-overlap.

This is the C counterpart of commit f5c9213e79bbe8ddbfa12a1b10b60cf3fb7618c1:
https://aomedia-review.googlesource.com/c/aom/+/76182

BUG=aomedia:1997

Change-Id: I020715366858d1de1af419b1ef43628e01c7b8b2

av1/common/convolve.c

diff --git a/av1/common/convolve.c b/av1/common/convolve.c
index 6b27c11..655b9cc 100644
--- a/av1/common/convolve.c
+++ b/av1/common/convolve.c
@@ -238,7 +238,7 @@
   (void)conv_params;
 
   for (int y = 0; y < h; ++y) {
-    memcpy(dst + y * dst_stride, src + y * src_stride, w * sizeof(src[0]));
+    memmove(dst + y * dst_stride, src + y * src_stride, w * sizeof(src[0]));
   }
 }
 
@@ -632,7 +632,7 @@
   (void)bd;
 
   for (int y = 0; y < h; ++y) {
-    memcpy(dst + y * dst_stride, src + y * src_stride, w * sizeof(src[0]));
+    memmove(dst + y * dst_stride, src + y * src_stride, w * sizeof(src[0]));
   }
 }