Fix the "Failed to open random seed ..." message.

Fix the "Failed to open random seed ..." message.

When boot ArchLinux from Ventoy, it always print `Failed to open random seed file: write protected.`
As Ventoy emulate the ISO file as a read-only CDROM, I didn't test with a real physical CDROM drive, but maybe it also has such problem.
As we use `EFI_FILE_MODE_WRITE`  to open the `loader\random-seed` file, so I think it's better to check the result with both  `EFI_WRITE_PROTECTED` and `EFI_NOT_FOUND`.