[rialto] Adjust the MMIO range mapped in page table

Bug: 284462758
Test: atest rialto_test
Test: m pvmfw_img
Change-Id: Iea45b48a5c5c023a43e1e2e396cbf7016f275ce1
diff --git a/vmbase/src/layout/crosvm.rs b/vmbase/src/layout/crosvm.rs
index fbeb477..85d1e0b 100644
--- a/vmbase/src/layout/crosvm.rs
+++ b/vmbase/src/layout/crosvm.rs
@@ -16,10 +16,14 @@
 //!
 //! https://crosvm.dev/book/appendix/memory_layout.html#common-layout
 
+use core::ops::Range;
+
 /// The start address of MMIO space.
 pub const MMIO_START: usize = 0x0;
 /// The end address of MMIO space.
 pub const MMIO_END: usize = 0x4000_0000;
+/// MMIO range.
+pub const MMIO_RANGE: Range<usize> = MMIO_START..MMIO_END;
 
 /// The start of the system's contiguous "main" memory.
 pub const MEM_START: usize = 0x8000_0000;