SeaVGABIOS/vbe: Query driver for scanline pitch v2

SeaVGABIOS/vbe: Query driver for scanline pitch v2

Query the driver for the real scanline pitch in bytes.

As cbvga doesn't change the pitch on mode change, always
return the same pitch, that might exceed width times Bytes-per-pixel.

Report the default stdvga pitch for all other drivers.

Signed-off-by: Patrick Rudolph <siro@das-labor.org>