Pass x0-x3 boot values to Rust main function.

Bug: 223166344
Test: Ran --unprotected-vm-with-firmware with patched crosvm.
Test: Ran unprotected VM with crosvm.
Change-Id: I1b7d795ab1964741dac1983d4503aa96de818964
diff --git a/pvmfw/src/main.rs b/pvmfw/src/main.rs
index d98ea8e..280e1ce 100644
--- a/pvmfw/src/main.rs
+++ b/pvmfw/src/main.rs
@@ -24,6 +24,10 @@
 main!(main);
 
 /// Entry point for pVM firmware.
-pub fn main() {
-    println!("Hello world");
+pub fn main(fdt_address: u64, payload_start: u64, payload_size: u64, arg3: u64) {
+    println!("pVM firmware");
+    println!(
+        "fdt_address={:#010x}, payload_start={:#010x}, payload_size={:#010x}, x3={:#010x}",
+        fdt_address, payload_start, payload_size, arg3,
+    );
 }