pyramid: Re-map memory to fix random reboots

This leaves userspace with 540MB of RAM.

Signed-off-by: Sultanxda <sultanxda@gmail.com>
sultan_defconfig: r48.8
pyramid: Undervolt display by 400mV

Credit to scverhagen for the idea.
sultan_defconfig: Use Grouper net configuration

This fixes VPN. All that was really needed was probably CONFIG_NF_CONNTRACK_IPV6, but my kernel is getting tcp-related watchdog barks so I decided to copy the Grouper's configuration almost completely.

Signed-off-by: Sultanxda <sultanxda@gmail.com>
sultan_defconfig: r49