bignum_mod_raw: Fixed a documentation typo.

Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
diff --git a/library/bignum_mod_raw.c b/library/bignum_mod_raw.c
index 3de5940..d29896c 100644
--- a/library/bignum_mod_raw.c
+++ b/library/bignum_mod_raw.c
@@ -154,7 +154,7 @@
             /* Optimised Reduction */
             (*N->rep.ored.modp)(T, T_limbs);
 
-            /* Convert back to cannonical representation */
+            /* Convert back to canonical representation */
             mbedtls_mpi_mod_raw_fix_quasi_reduction(T, N);
             memcpy(X, T, N->limbs * sizeof(mbedtls_mpi_uint));
             break;