system/uart: refactor debug_uart, fix arm uart

* Drop ArchUART8260 layer to reduce complexity. It's whole
  existance in life was to adjust the mmio alignment.
* Fold architecture mmio alignment into DebugUart
* We could potentially pass a Init(int mmioAlignment)
  arg in the future if the macros get too messy.
* Move Barrier code back a layer into DebugUART
* Fixes the arm uart and EFI build

Change-Id: I0f127d902993e9f6e6a03cac8c7c37c0363134bf
Reviewed-on: https://review.haiku-os.org/c/haiku/+/4422
Reviewed-by: Alex von Gluck IV <[email protected]>
Reviewed-by: waddlesplash <[email protected]>
Tested-by: Commit checker robot <[email protected]>

headers/private/kernel/arch/generic/debug_uart.h

@@ -40,12 +40,9 @@ public:
 			bool			Enabled() const { return fEnabled; }
 
 protected:
-	// default MMIO
-	virtual	void			Out8(int reg, uint8 value)
-								{ *((uint8 *)Base() + reg) = value; }
-	virtual	uint8			In8(int reg)
-								{ return *((uint8 *)Base() + reg); }
-	virtual	void			Barrier() {}
+	virtual	void			Out8(int reg, uint8 value);
+	virtual	uint8			In8(int reg);
+	virtual	void			Barrier();
 
 private:
 			addr_t			fBase;

headers/private/kernel/arch/generic/debug_uart_8250.h

@@ -34,8 +34,6 @@ public:
 
 			void			FlushTx();
 			void			FlushRx();
-
-	virtual	void			Barrier();
 };