mgmt: mcumgr: grp: os_mgmt: Change select to imply for reboot

OS management's reset is optional, therefore only imply reset
instead of selecting it, so it can optionally disabled if not
needed.

Signed-off-by: Jamie McCrae <jamie.mccrae@nordicsemi.no>
diff --git a/subsys/mgmt/mcumgr/grp/os_mgmt/Kconfig b/subsys/mgmt/mcumgr/grp/os_mgmt/Kconfig
index 951ac18..36391ac 100644
--- a/subsys/mgmt/mcumgr/grp/os_mgmt/Kconfig
+++ b/subsys/mgmt/mcumgr/grp/os_mgmt/Kconfig
@@ -14,12 +14,14 @@
 
 menuconfig MCUMGR_GRP_OS
 	bool "Mcumgr handlers for OS management"
-	select REBOOT
+	imply REBOOT
 	help
 	  Enables MCUmgr handlers for OS management
 
 if MCUMGR_GRP_OS
 
+if REBOOT
+
 config MCUMGR_GRP_OS_RESET_MS
 	int "Delay before executing reset command (ms)"
 	default 250
@@ -42,6 +44,8 @@
 	  and will allow the application to perform any required operations
 	  before accepting or declining the reset request.
 
+endif
+
 config MCUMGR_GRP_OS_TASKSTAT
 	bool "Support for taskstat command"
 	depends on THREAD_MONITOR