Clear a first pass motion search corner case

This is a port from libvpx and speculative fix for b/476473849. A repro
has not been found yet.
dca6330a24 Clear a first pass motion search corner case

When setting the motion search parameters, align the frame size
to be same or above a coding block size for consistency with other
related use cases in the encoder.

Bug: 476473849
Change-Id: Ib6de89c41f9e8e1569916a3167b5d1c5a63c8f1d

av1/encoder/firstpass.c

diff --git a/av1/encoder/firstpass.c b/av1/encoder/firstpass.c
index a49db4a..0c66d7f 100644
--- a/av1/encoder/firstpass.c
+++ b/av1/encoder/firstpass.c
@@ -256,7 +256,8 @@
 // for first pass test.
 static int get_search_range(int width, int height) {
   int sr = 0;
-  const int dim = AOMMIN(width, height);
+  int dim = AOMMIN(width, height);
+  dim = AOMMAX(dim, MI_SIZE);
 
   while ((dim << sr) < MAX_FULL_PEL_VAL) ++sr;
   return sr;