doc: release-notes: Update release notes 3.4

Update release notes 3.4 with the new FatFs reentrant Kconfig option.

Signed-off-by: Nicola Ochsenbein <[email protected]>

Author: Ox11

doc/releases/release-notes-3.4.rst

@@ -324,6 +324,10 @@ Devicetree
 Libraries / Subsystems
 **********************
 
+* File systems
+
+  * Added :kconfig:option:`CONFIG_FS_FATFS_REENTRANT` to enable the FAT FS reentrant option.
+
 HALs
 ****