scripts: Always use the RNG device with QEMU

There is no harm in always having this device enabled, thus reducing the
number of script arguments. Enable RNG always.

Series-to: concept
Series-version: 2
Series-changes: 2
- Use /dev/urandom instead, dropping the now-unnecessary arguments

Signed-off-by: Simon Glass <sjg@chromium.org>
Suggested-by: Heinrich Schuchardt <xypron.glpk@gmx.de>

scripts/build_helper.py

@@ -178,10 +178,8 @@ sct_mnt = /mnt/sct
                 else:
                     tout.warning(f"Disk image '{disk}' not found")
 
-        if args.rand:
-            cmd.extend(['-object', 'rng-random,filename=/dev/random,id=rng0',
-                        '-device',
-                        'virtio-rng-pci,rng=rng0,max-bytes=1024,period=1000'])
+        cmd.extend(['-object', 'rng-random,filename=/dev/urandom,id=rng0',
+                    '-device', 'virtio-rng-pci,rng=rng0'])
 
 def add_common_args(parser):
     """Add some arguments which are common to build-efi/qemu scripts
@@ -211,8 +209,6 @@ def add_common_args(parser):
     parser.add_argument(
         '-R', '--release', default='24.04.1',
         help='Select OS release version (e.g, 24.04) Default: 24.04.1')
-    parser.add_argument('--rand', '--random', action='store_true',
-                        help='Provide a random-number device')
     parser.add_argument('-s', '--serial-only', action='store_true',
                         help='Run QEMU with serial only (no display)')
     parser.add_argument(