Zephyr 3.5 moved the RAM disk driver from Kconfig to devicetree and 4.1
replaced CONFIG_NET_SOCKETS_POSIX_NAMES with CONFIG_POSIX_API. Port the
sample to the new APIs while keeping it buildable on older Zephyr.
- add ramdisk.overlay (zephyr,ram-disk node) for the FS scenarios;
drop CONFIG_DISK_RAM_VOLUME_SIZE
- switch to CONFIG_POSIX_API; include the POSIX time/select/socket/netdb
headers in test.h and port.h, gated on ZEPHYR_VERSION_CODE >= 4.1.0 so
older Zephyr keeps the BSD names from <zephyr/net/socket.h>
- select RAM disk (overlay >= 3.5, else CONFIG_DISK_RAM_VOLUME_SIZE) and
POSIX (CONFIG_POSIX_API >= 4.1, else the legacy symbols) in
CMakeLists.txt, with ramdisk_legacy.conf / posix_legacy.conf fallbacks
- tests, nofs and kbi scenarios pass on qemu_x86 with Zephyr 3.4.0
(SDK 0.16.1) and 4.4.0 (SDK 1.0.0)