Meadow.Linux: Add support for Raspberry Pi 5 pinout

The Raspberry Pi 5 pinout is quite different from the previous
versions, so we need to add a new pinout class for it. It use a
in house developed silicon for I/O, the RP1 I/O controller. It's
comes with a new pinctrl driver that changed the sysfs base from
0 to 53 and the gpiochip bank from gpiochip0 to gpiochip4.

However, reusing what we already have from previous versions of
Raspberry Pi, we can support this simply by modifying
the LinuxFlexiPin to allow changing the SysFsGpio and
GpiodChip.

Signed-off-by: Matheus Castello <matheus.castello@toradex.com>

source/implementations/linux/Meadow.Linux/Hardware/Pinouts/RaspberryPi5.cs

@@ -0,0 +1,19 @@
+using Meadow.Hardware;
+using System.Collections;
+using System.Collections.Generic;
+
+namespace Meadow.Pinouts
+{
+    public class RaspberryPi5 : RaspberryPi
+    {
+        public RaspberryPi5()
+        {
+            // the sysfs base for the pinctrl-rpi1 is 53
+            // the gpiochip bank for pinctrl-rpi1 on rpi5 is gpiochip4
+            foreach (LinuxFlexiPin pin in this.AllPins) {
+                pin.SysFsGpio += 53;
+                pin.GpiodChip = "gpiochip4";
+            }
+        }
+    }
+}

source/implementations/linux/Meadow.Linux/SysFs/LinuxFlexiPin.cs

@@ -11,11 +11,11 @@ public class LinuxFlexiPin : Pin
         /// <summary>
         /// The pin's sysfs GPIO number
         /// </summary>
-        public int SysFsGpio { get; }
+        public int SysFsGpio { get; internal set; }
         /// <summary>
         /// The chip name for the gpiod driver
         /// </summary>
-        public string GpiodChip { get; }
+        public string GpiodChip { get; internal set; }
         /// <summary>
         /// The pin offset for the gpiod driver
         /// </summary>