#145: Fix CMOS handling

[coreboot]

#145: Fix CMOS handling
---------------------------------+------------------------------------------
   Reporter:  oxygene            |          Owner:  somebody
       Type:  defect             |         Status:  new     
   Priority:  minor              |      Milestone:          
  Component:  coreboot           |        Version:  v2      
   Keywords:                     |   Dependencies:          
Patchstatus:  there is no patch  |  
---------------------------------+------------------------------------------
 CMOS handling isn't very good at this time.

Example:
 The fallback image uses hardcoded values for serial port configuration,
 normal image uses CMOS values.

If normal is booted, and the CMOS values are invalid, serial is dead, and
 the boot might misbehave as the wrong IO port is used.

Alternative: Compile a defaults table for CMOS values, and use that if the
 checksum of the CMOS data is wrong (and maybe even unconditionally in
 fallback)

But, do not overwrite CMOS with that table, as the data in there should
 probably stay (eg. when switching between vendor BIOS and coreboot in
 testing scenarios). Just use that table as an alternative data source.

This could also eliminate a couple of #ifs, if the non-CMOS variant of
 code just uses the default table.

Marked as "defect", as the broken serial console actually happened several
 times, and confused people. The proposed solution is an enhancement, but
 nevermind...