test: do not rely on => being the prompt

In our tests we should use the customized prompt for testing.

Reported-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Tested-by: Tom Rini <trini@konsulko.com>
diff --git a/test/py/tests/test_efi_loader.py b/test/py/tests/test_efi_loader.py
index ca68626..fc8d6b8 100644
--- a/test/py/tests/test_efi_loader.py
+++ b/test/py/tests/test_efi_loader.py
@@ -199,6 +199,6 @@
     # Then exit cleanly
     u_boot_console.wait_for('grub>')
     u_boot_console.run_command('exit', wait_for_prompt=False, wait_for_echo=False)
-    u_boot_console.wait_for('=>')
+    u_boot_console.wait_for(u_boot_console.prompt)
     # And give us our U-Boot prompt back
     u_boot_console.run_command('')