Kconfig logic for disks

[Laczen]

At the moment the Kconfig logic for disks is using CONFIG_DISK_ACCESS as a "driver" to select CONFIG_DISK_DRIVERS and to get the correct disk driver in the code. Also the DT_HAS_..._ENABLED mechanism is used to enable the correct driver from devicetree.

Would it not be better to use the DT_HAS_..._ENABLED mechanism to select the driver and to use imply DISK_ACCESS in each of the driver Kconfigs (as each of the drivers is using disk_access_register)?

@danieldegrasse, @jfischer-no