This updates Cortex-M3 port files to version found in
V10.3.1-kernel-only tag of FreeRTOS-Kernel.
The new upstream release includes memory barriers which are essential
for use with modern optimising compilers. Without those firmware
certainly breaks with -O3 -flto and might be also broken with other
optimisation configurations.
Fixes: d59ec10c4e ("Update FreeRTOS to v10.3.1")
76099406ef