[rialto] Adjust FDT size in initialization

And also:
- Add the FDT_SIZE const to vmbase.
- Reuse the const in both rialto and pvmfw.

No behavior change for pvmfw.

Bug: 284462758
Test: atest rialto_test
Test: m pvmfw_img
Change-Id: I39700d9c87bb1edf71a5a8006fc8d0851c2e183a
diff --git a/rialto/src/main.rs b/rialto/src/main.rs
index 3328659..11ca570 100644
--- a/rialto/src/main.rs
+++ b/rialto/src/main.rs
@@ -37,7 +37,6 @@
 
 const SZ_1K: usize = 1024;
 const SZ_64K: usize = 64 * SZ_1K;
-const SZ_1M: usize = 1024 * SZ_1K;
 
 #[global_allocator]
 static HEAP_ALLOCATOR: LockedHeap<32> = LockedHeap::<32>::new();
@@ -90,7 +89,7 @@
 unsafe fn try_main(fdt_addr: usize) -> Result<()> {
     info!("Welcome to Rialto!");
     // SAFETY: The caller ensures that `fdt_addr` is valid.
-    let fdt = unsafe { slice::from_raw_parts(fdt_addr as *mut u8, SZ_1M) };
+    let fdt = unsafe { slice::from_raw_parts(fdt_addr as *mut u8, crosvm::FDT_MAX_SIZE) };
     let fdt = libfdt::Fdt::from_slice(fdt)?;
     let pci_info = PciInfo::from_fdt(fdt)?;
     debug!("PCI: {:#x?}", pci_info);