Fix spelling and typographical errors found by cspell

Signed-off-by: Tom Cosgrove <tom.cosgrove@arm.com>
diff --git a/include/mbedtls/rsa.h b/include/mbedtls/rsa.h
index ca0c6e1..062df73 100644
--- a/include/mbedtls/rsa.h
+++ b/include/mbedtls/rsa.h
@@ -687,7 +687,7 @@
  *                   mode being set to #MBEDTLS_RSA_PRIVATE and might instead
  *                   return #MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED.
  *
- * \param ctx        The initnialized RSA context to use.
+ * \param ctx        The initialized RSA context to use.
  * \param f_rng      The RNG function to use. This is needed for padding
  *                   generation and must be provided.
  * \param p_rng      The RNG context to be passed to \p f_rng. This may