arch/arm/src/lpc2378/Kconfig: Create Kconfig for the platform; Adjust configuration names for compatibility,  configs/olimex-lpc2378/nsh: Convert to use the kconfig-frontends tools

Remove some OS test configurations.  These don't have much value after the initial bring-up (and are certainly not worth converting to kconfig-frontends tools).

Set CONFIG_DEFAULT_SMALL=y in the defconfig for all smaller MCUs so that if they are reconfigured, they will pick up the most conservative options for all new settings

configs/*/defconfig:  If CONFIG_NSH_LIBRARY is set, make sure that CONFIG_NSH_READLINE is also set or the configuration will use the CLE the next time it is reconfigured