dell/e6400nvidia: switch to "normal" config

vgarom configs no longer execute vga roms from seabios,
and coreboot is set to not do so either.

therefore, this config should now be named normal.

new path:

resources/coreboot/e6400nvidia_4mb/config/normal

old path:

resources/coreboot/e6400nvidia_4mb/config/vgarom_txtmode

In "normal" configs, text mode is assumed, and hardcoded
in lbmk. It is assumed that a VGA ROM would be provided, that
handles everything (meaning, not SeaVGABIOS).

Also, this commit fixes VGA init on E6400 Nvidia, in case
it's not clear. The last few patches broke it, for reasons
explained above.