allow docker_inram to kernel cmd list (sonic-net#15374)

Why I did it
After docker_inram is enabled, the docker folder's default max size is 1.5G.
It's not big enough for some tests which need to install additional docker images or install extra packages.

Work item tracking
Microsoft ADO 24199761:
How I did it
add docker_inram into cmdline_allowlist

How to verify it
sudo sh -c 'echo "docker_inram_size=3000M" >> kernel-cmdline-append'
sudo reboot and check the docker folder size

Author: lipxu

files/Aboot/boot0.j2

@@ -86,7 +86,7 @@ installer_image_path="$image_path/$installer_image"
 
 boot_config="$target_path/boot-config"
 
-cmdline_allowlist="crashkernel hwaddr_ma1 sonic_fips"
+cmdline_allowlist="crashkernel hwaddr_ma1 sonic_fips docker_inram"
 
 # for backward compatibility with the sonic_upgrade= behavior
 install="${install:-${sonic_upgrade:-}}"