Fix spelling and typographical errors found by cspell

Signed-off-by: Tom Cosgrove <tom.cosgrove@arm.com>
diff --git a/include/mbedtls/bignum.h b/include/mbedtls/bignum.h
index 9d2cff3..dd594c5 100644
--- a/include/mbedtls/bignum.h
+++ b/include/mbedtls/bignum.h
@@ -989,7 +989,7 @@
  *                 generate yourself and that are supposed to be prime, then
  *                 \p rounds should be at least the half of the security
  *                 strength of the cryptographic algorithm. On the other hand,
- *                 if \p X is chosen uniformly or non-adversially (as is the
+ *                 if \p X is chosen uniformly or non-adversarially (as is the
  *                 case when mbedtls_mpi_gen_prime calls this function), then
  *                 \p rounds can be much lower.
  *