arima mainboard config

[ron minnich]

I find this in the arima mainboard config:
 ## ROM_SIZE is the size of boot ROM that this board will use.
option ROM_SIZE = 524288



This is the wrong place. ROM_SIZE should always be in the target config 
file, not the mainboard config file.

Recall that we no longer allow multiple settings of options, as a way of 
avoiding the "where did it get set last" syndrome. You only get to set 
them once. (we also disallow set-after-use, BTW).

You can default them. I also note that in Options.lb, we are currently 
defaulting ROM_SIZE to 262144, also a mistake (mine). 

So what we need to do:

in src/config/Options.lb, ROM_SIZE should have no default value. 

If you really want a default size for ROM_SIZE in the mainboard config, 
then 

default ROM_SIZE = 524288

in the mainboard file

that way, for all my arimas on which I am using 1 MB parts, I can set 
option ROM_SIZE = 1024*1024
in my target config file.

If no objections, I am going to remove the default setting in Options.lb, 
make the mainboard ROM_SIZE settings defaults, so I can continue to set 
them in the target config files.

thanks

ron