samples: fs: Enable littlefs sample for mimxrt685_evk.

Add mimxrt685_evk_cm33 board to the platform_allow list
for the littlefs sample application.

Signed-off-by: Saurabh Jagdhane <[email protected]>

Author: saurabh-nxp

samples/subsys/fs/littlefs/sample.yaml

@@ -4,5 +4,5 @@ tests:
   sample.filesystem.littlefs:
     build_only: true
     platform_allow: nrf52840dk_nrf52840 particle_xenon disco_l475_iot1
-      mimxrt1060_evk mimxrt1064_evk qemu_x86 native_posix
+      mimxrt685_evk_cm33 mimxrt1060_evk mimxrt1064_evk qemu_x86 native_posix
     tags: filesystem