disk: simplify print_part_header()

Using uclass_get_name() reduces the code size.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/test/py/tests/test_scsi.py b/test/py/tests/test_scsi.py
index be2e283..445693c 100644
--- a/test/py/tests/test_scsi.py
+++ b/test/py/tests/test_scsi.py
@@ -87,6 +87,6 @@
 def test_scsi_part(u_boot_console):
     test_scsi_dev(u_boot_console)
     output = u_boot_console.run_command('scsi part')
-    assert 'Partition Map for SCSI device' in output
+    assert 'Partition Map for scsi device' in output
     output = u_boot_console.run_command('echo $?')
     assert output.endswith('0')