[Mellanox] Addition of minicom configuration file (#19234)

- Why I did it
For setting the rts and cts configuration for the minicom package to the switch image, The file is copied to minicom configuration location in the switch image
This is a machine generated file in minicom , so the configuration can be present in the switch image upon installation

files/build_templates/sonic_debian_extension.j2

@@ -1075,6 +1075,8 @@ sudo LANG=C chroot $FILESYSTEM_ROOT systemctl enable nv-syncd-shared
 
 # Install required packages specific for mellanox platform
 sudo LANG=C DEBIAN_FRONTEND=noninteractive chroot $FILESYSTEM_ROOT apt-get -y install minicom xmlstarlet
+sudo mkdir -p $FILESYSTEM_ROOT/etc/minicom/
+sudo cp platform/mellanox/minirc.dfl $FILESYSTEM_ROOT/etc/minicom/
 
 sudo LANG=C chroot $FILESYSTEM_ROOT systemctl disable rshim.service
 {% endif %}

platform/mellanox/minirc.dfl

@@ -0,0 +1,2 @@
+# Machine-generated file - use "minicom -s" to change parameters.
+pu rtscts           No