PL011 uart: rename UART -> uart

* Left over var name from my test code
* This should be pretty close to functional
  (if not already working)
* Any more uart experimentation will not
  reach upstream until working.

src/system/kernel/arch/arm/uart_pl011.cpp

@@ -82,8 +82,8 @@ UartPL011::InitPort(uint32 baud)
 	// Calculate baud divisor
 	uint32 baudDivisor = BOARD_UART_CLOCK / (16 * baud);
 	uint32 remainder = BOARD_UART_CLOCK % (16 * baud);
-	uint32 baudFractional = ((8 * remainder) / BAUD >> 1)
-		+ ((8 * remainder) / BAUD & 1);
+	uint32 baudFractional = ((8 * remainder) / baud >> 1)
+		+ ((8 * remainder) / baud & 1);
 
 	// Disable UART
 	Disable();