disk: kconfig: Group related symbols and use 'menuconfig' symbol
disk: kconfig: Group related symbols and use 'menuconfig' symbol

Put the symbols that depend on DISK_ACCESS_{RAM,FLASH,SDHC} directly
after the symbol they depend on, so that they end up in an implicit
indented menu. That makes it easier to see which symbols are related.

It also indirectly makes all symbols children of DISK_ACCESS. To save a
menu level, turn DISK_ACCESS into a 'menuconfig' symbol and put it in
the top-level menu. Change its prompt from "Enable Disk Interface" to
"Disk Interface", to be consistent with e.g. "Logging".

Signed-off-by: Ulf Magnusson <01743f1c1deb1fe75271d62edb65757d98ac0bcb@nordicsemi.no>

galak/zephyr,galak/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,finikorg/zephyr,nashif/zephyr,GiulianoFranchetto/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,Vudentz/zephyr,Vudentz/zephyr,finikorg/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,finikorg/zephyr,nashif/zephyr,Vudentz/zephyr,galak/zephyr,Vudentz/zephyr,galak/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr