test/py: gpt: Use long options for sgdisk

sgdisk 0.8.10.2 from AOSP doesn't support short options, failing with
errors like this:

    sgdisk: invalid option -- 'U'

Test fails due to that error. Let's use long options to make the test
work with any sgdisk version.

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Acked-by: Stephen Warren <swarren@nvidia.com>
diff --git a/test/py/tests/test_gpt.py b/test/py/tests/test_gpt.py
index c8edb33..229d7eb 100644
--- a/test/py/tests/test_gpt.py
+++ b/test/py/tests/test_gpt.py
@@ -40,16 +40,19 @@
                 fd = os.open(persistent, os.O_RDWR | os.O_CREAT)
                 os.ftruncate(fd, 4194304)
                 os.close(fd)
-                cmd = ('sgdisk', '-U', '375a56f7-d6c9-4e81-b5f0-09d41ca89efe',
+                cmd = ('sgdisk',
+                    '--disk-guid=375a56f7-d6c9-4e81-b5f0-09d41ca89efe',
                     persistent)
                 u_boot_utils.run_and_log(u_boot_console, cmd)
                 # part1 offset 1MB size 1MB
-                cmd = ('sgdisk', '--new=1:2048:4095', '-c 1:part1', persistent)
+                cmd = ('sgdisk', '--new=1:2048:4095', '--change-name=1:part1',
+                    persistent)
                 # part2 offset 2MB size 1.5MB
                 u_boot_utils.run_and_log(u_boot_console, cmd)
-                cmd = ('sgdisk', '--new=2:4096:7167', '-c 2:part2', persistent)
+                cmd = ('sgdisk', '--new=2:4096:7167', '--change-name=2:part2',
+                    persistent)
                 u_boot_utils.run_and_log(u_boot_console, cmd)
-                cmd = ('sgdisk', '-l', persistent)
+                cmd = ('sgdisk', '--load-backup=' + persistent)
                 u_boot_utils.run_and_log(u_boot_console, cmd)
 
         cmd = ('cp', persistent, self.path)