mgmt/mcumgr: Add mising static to zephyr_smp_alloc_rsp
mgmt/mcumgr: Add mising static to zephyr_smp_alloc_rsp

The commit adds missing static to the zephyr_smp_alloc_rsp
function definition; it also reorders some of definitions
and removes no longer needed block of forward declarations
of functions.

Signed-off-by: Dominik Ermel <1a1d45a9cc0c98a37f8d0a0d2dbe3cacc0b2344f@nordicsemi.no>

zephyrproject-rtos/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,finikorg/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,finikorg/zephyr