NAND: Add CFG_NAND_QUIET option

This config option sets the default for the progress information
output behavior that can also be configured through the 'quiet'
environment variable.

The legacy NAND code does not print the current progress info
on the console. So this option is for backward compatibility for
units that are in the field and where setting the quiet variable
is not an option. With CFG_NAND_QUIET set to '1' the console
progress info is turned off. This can still be overwritten
through the environment variable.

Signed-off-by: Matthias Fuchs <matthias.fuchs@esd-electronics.com>