Redo of PR#5345. Fixed spelling and typographical errors found by CodeSpell.

Signed-off-by: Shaun Case <warmsocks@gmail.com>
Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/library/rsa.c b/library/rsa.c
index 497fc21..6a9e402 100644
--- a/library/rsa.c
+++ b/library/rsa.c
@@ -848,10 +848,10 @@
  * the more bits of the key can be recovered. See [3].
  *
  * Collecting n collisions with m bit long blinding value requires 2^(m-m/n)
- * observations on avarage.
+ * observations on average.
  *
  * For example with 28 byte blinding to achieve 2 collisions the adversary has
- * to make 2^112 observations on avarage.
+ * to make 2^112 observations on average.
  *
  * (With the currently (as of 2017 April) known best algorithms breaking 2048
  * bit RSA requires approximately as much time as trying out 2^112 random keys.