mainboard/*/*/ec.c: Do not include `chromeos/chromeos.h`

It's not needed and causes build failures without CONFIG_CHROMEOS.

Change-Id: I7923717bfc5c84698044008e5f2441206041e0dd
Reported-by: Idwer Vollering <vidwer@gmail.com>
Signed-off-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-on: http://review.coreboot.org/5398
Reviewed-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@google.com>