libfdt: Extend Rust wrapper with write functions

Add a subset of the libfdt "read-write" function to the Rust wrapper.

Bug: 255521657
Test: atest vmbase_example.integration_test
Change-Id: Id73e823d7f522431c8f9dd23799841317a9ce38a
diff --git a/vmbase/example/idmap.S b/vmbase/example/idmap.S
index 7fc5d5e..71a6ade 100644
--- a/vmbase/example/idmap.S
+++ b/vmbase/example/idmap.S
@@ -44,7 +44,7 @@
 	.fill		509, 8, 0x0			// 509 GiB of remaining VA space
 
 	/* level 2 */
-0:	.quad		.L_BLOCK_RO  | 0x80000000	// DT provided by VMM
+0:	.quad		.L_BLOCK_MEM | 0x80000000	// DT provided by VMM
 	.quad		.L_BLOCK_MEM_XIP | 0x80200000	// 2 MiB of DRAM containing image
 	.quad		.L_BLOCK_MEM | 0x80400000	// 2 MiB of writable DRAM
 	.fill		509, 8, 0x0