cmd: cat: add new command

Add cat command to print file content to standard out

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Roger Knecht <rknecht@pm.me>

test/py/tests/test_cat/test_cat.py

@@ -0,0 +1,20 @@
+# SPDX-License-Identifier:      GPL-2.0+
+
+""" Unit test for cat command
+"""
+
+import pytest
+
+@pytest.mark.boardspec('sandbox')
+@pytest.mark.buildconfigspec('cmd_cat')
+def test_cat(u_boot_console, cat_data):
+    """ Unit test for cat
+
+    Args:
+        u_boot_console -- U-Boot console
+        cat_data -- Path to the disk image used for testing.
+    """
+    response = u_boot_console.run_command_list([
+        f'host bind 0 {cat_data}',
+        'cat host 0 hello'])
+    assert 'hello world' in response