Remove the now impossible BN_R_NOT_INITIALIZED check in BN_div

This was just checking the bn_correct_top invariant. But since we got
rid of the bn_correct_top invariant and dynamically compute
bn_minimal_width anyway, bn_minimal_width will always be computed such
that the check succeeds.

Bug: 358687140
Change-Id: Idc1abbc46c38d47f319ee5835a5a601a8a3d9c0e
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/70171
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: Bob Beck <bbe@google.com>

crypto/fipsmodule/bn/div.c

diff --git a/crypto/fipsmodule/bn/div.c b/crypto/fipsmodule/bn/div.c
index 0410fb7..06bc4f8 100644
--- a/crypto/fipsmodule/bn/div.c
+++ b/crypto/fipsmodule/bn/div.c
@@ -198,15 +198,6 @@
   BN_ULONG d0, d1;
   int num_n, div_n;
 
-  // Invalid zero-padding would have particularly bad consequences.
-  int numerator_width = bn_minimal_width(numerator);
-  int divisor_width = bn_minimal_width(divisor);
-  if ((numerator_width > 0 && numerator->d[numerator_width - 1] == 0) ||
-      (divisor_width > 0 && divisor->d[divisor_width - 1] == 0)) {
-    OPENSSL_PUT_ERROR(BN, BN_R_NOT_INITIALIZED);
-    return 0;
-  }
-
   if (BN_is_zero(divisor)) {
     OPENSSL_PUT_ERROR(BN, BN_R_DIV_BY_ZERO);
     return 0;