Replace stale tutorial reference links

Tutorial/phase-07-uart-mmio/phase-07-03-bus-decoder-mmio.md

@@ -43,6 +43,6 @@ semantics becomes painful. Document behavior precisely.
 
 ## References
 
-- OSDev MMIO overview: https://wiki.osdev.org/Memory_Mapped_Registers_in_C/C%2B%2B
+- Memory-mapped I/O overview: https://en.wikipedia.org/wiki/Memory-mapped_I/O
 - RISC-V privileged spec for access faults later: https://riscv.org/technical/specifications/
 - AXI-Lite valid/ready concepts for comparison: https://developer.arm.com/documentation/ihi0022/latest

Tutorial/phase-07-uart-mmio/phase-07.md

@@ -45,5 +45,4 @@ and peripheral register file translate those into device behavior.
 
 - Digilent Arty A7 USB-UART notes: https://digilent.com/reference/programmable-logic/arty-a7/reference-manual
 - RISC-V platform-level interrupt spec for later context: https://github.com/riscv/riscv-plic-spec
-- OSDev MMIO overview: https://wiki.osdev.org/Memory_Mapped_Registers_in_C/C%2B%2B
-
+- Memory-mapped I/O overview: https://en.wikipedia.org/wiki/Memory-mapped_I/O