Fix yet another occasions of 'setup' vs. 'set up' typo in x509_crt.h
diff --git a/include/mbedtls/x509_crt.h b/include/mbedtls/x509_crt.h
index 77609ef..2fb26fd 100644
--- a/include/mbedtls/x509_crt.h
+++ b/include/mbedtls/x509_crt.h
@@ -664,7 +664,7 @@
                                 mbedtls_x509_crt_frame *dst );
 
 /**
- * \brief           Setup a PK context with the public key in a certificate.
+ * \brief           Set up a PK context with the public key in a certificate.
  *
  * \param crt       The certificate to use. This must be initialized and set up.
  * \param pk        The address of the destination PK context to fill.