Fix typos

Signed-off-by: Tom Cosgrove <tom.cosgrove@arm.com>
diff --git a/scripts/mbedtls_dev/bignum_mod_raw.py b/scripts/mbedtls_dev/bignum_mod_raw.py
index 461b1f2..ae855e8 100644
--- a/scripts/mbedtls_dev/bignum_mod_raw.py
+++ b/scripts/mbedtls_dev/bignum_mod_raw.py
@@ -64,7 +64,7 @@
     input_style = "arch_split"
     arity = 1
     suffix = True
-    mongtomgery_form_a = True
+    montgomery_form_a = True
     disallow_zero_a = True
 
     def result(self) -> List[str]: