Add driver for PIC32MX

Related to #789

Add a new driver for the PIC32MX chip in FreeRTOS Plus TCP.

* **BufferAllocation_2.c**
  - Include necessary headers for buffer allocation.
  - Implement buffer allocation functions for PIC32MX.
* **NetworkInterface_eth.c**
  - Include necessary headers for Ethernet driver.
  - Implement Ethernet driver functions for PIC32MX.
* **CMakeLists.txt**
  - Add CMake configuration for PIC32MX Ethernet driver.

Author: vishwamartur

source/portable/NetworkInterface/CMakeLists.txt

@@ -47,6 +47,7 @@ add_subdirectory(MPS4_CS315)
 add_subdirectory(NXP1060)
 add_subdirectory(mw300_rd)
 add_subdirectory(pic32mzef)
+add_subdirectory(pic32mx)
 add_subdirectory(RX)
 add_subdirectory(SH2A)
 add_subdirectory(STM32Fxx)