integrator: update the Integrator/CP config

integrator: update the Integrator/CP config

The Integrator/CP config file was very outdated and gives a
non functional U-Boot. So:

- Set the CONFIG_ARCH_CINTEGRATOR arch flag correctly
- Add proper core module configuration options
- Skip cluttered command lista and just include
  <config_cmd_default.h>
- Kill off #if 0 network section and insert some example
  configuration that simply just boots from the network
  using TFTP if available.
- Delete flash control registers that have no business
  in this config file. These are already moved down to
  board/armltd/integrator/integrator-sc.h

Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>