vmbase: Fully absorb libfdtpci as a crate module

Merge the library into libvmbase as a module. Given that clients were
already converted to using libfdtpci indirectly through libvmbase, they
should not be affected by this change.

Note: TEST_MAPPING is removed as duplicating libs/vmbase/TEST_MAPPING

Test: m
Change-Id: If38cd6b55681c29a20086861dd9b9e475f0265fd
diff --git a/libs/libvmbase/src/fdt.rs b/libs/libvmbase/src/fdt.rs
index 8618acd..ff0eaf0 100644
--- a/libs/libvmbase/src/fdt.rs
+++ b/libs/libvmbase/src/fdt.rs
@@ -14,6 +14,8 @@
 
 //! High-level FDT functions.
 
+pub mod pci;
+
 use core::ops::Range;
 use cstr::cstr;
 use libfdt::{self, Fdt, FdtError};
@@ -52,8 +54,3 @@
         self.addr.map(|addr| addr..addr + self.size)
     }
 }
-
-/// Library for working with (VirtIO) PCI devices discovered from a device tree.
-pub mod pci {
-    pub use fdtpci::*;
-}