doc: pytest: Document the test_efi_loader test

Add this test to the documentation. We need to add a code-block
annotation to the example and indent it correctly. We also need to
document the do_test_efi_helloworld_net function and that in turn means
changing the documentation to test_efi_helloworld_net_http and
test_efi_helloworld_net_tftp to reflect what is and isn't done in those
functions themselves now.

Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/doc/develop/pytest/index.rst b/doc/develop/pytest/index.rst
index 5bcda1f..3265eb9 100644
--- a/doc/develop/pytest/index.rst
+++ b/doc/develop/pytest/index.rst
@@ -19,5 +19,6 @@
 
    test_000_version
    test_bootstage
+   test_efi_loader
    test_net
    test_net_boot