arm: integrator: Migrate platform-specific options and cleanup armcoremodule.h

arm: integrator: Migrate platform-specific options and cleanup armcoremodule.h

This converts the following to Kconfig:
   CONFIG_CM_INIT
   CONFIG_CM_REMAP
   CONFIG_CM_SPD_DETECT
   CONFIG_CM_MULTIPLE_SSRAM
   CONFIG_CM_TCRAM

We make the first three of these options be always enabled, as that
matches usage.  We select the last two based on how they were defined in
armcoremodule.h.  This also allows us to remove some unused code in
board/armltd/integrator/lowlevel_init.S

Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Tom Rini <trini@konsulko.com>