smp_shell: Add missing include for k_fifo

The smp_shell module uses k_fifo, but does not include the kernel header
file that defines it. This commit adds the missing include.

Signed-off-by: Måns Ansgariusson <[email protected]>

Author: Mattemagikern

include/zephyr/mgmt/mcumgr/transport/smp_shell.h

@@ -11,6 +11,7 @@
 #ifndef ZEPHYR_INCLUDE_MGMT_SMP_SHELL_H_
 #define ZEPHYR_INCLUDE_MGMT_SMP_SHELL_H_
 
+#include <zephyr/kernel.h>
 #include <zephyr/types.h>
 
 #ifdef __cplusplus