liblp: Fix incorrect get_block_device_size usage.

Bug: 79173901
Test: N/A
Change-Id: I22a3e86153830782453a47e460800f3cb4c26958

fs_mgr/liblp/utility.cpp

@@ -38,7 +38,8 @@ bool GetDescriptorSize(int fd, uint64_t* size) {
     }
 
     if (S_ISBLK(s.st_mode)) {
-        return get_block_device_size(fd);
+        *size = get_block_device_size(fd);
+        return *size != 0;
     }
 
     int64_t result = SeekFile64(fd, 0, SEEK_END);