firmware: Remove Max3421E reset signal

Already using the CHIPRES bit to reset the device.
firmware: Add #defines for text rendering resources
firmware: Rename text module to "display"
DuinoCube: Add macro for adjusting large VRAM offsets
firmware: display module tracks VRAM usage
DuinoCube: Add VRAM bank computation macros
firmware: Load background image
DuinoCube: Fix color key register name in comment