zephyr: added ISB after cortex control was set

After modifying the CONTROL register, ISB function should be
used to ensure the effect of the change applies to
subsequent code.
Due to the simple nature of the Cortex-M3, Cortex-M4, Cortex-M0+,
Cortex-M0, and Cortex-M1 pipeline,
omission of the ISB instruction does not cause any problem.
But might cause problem on a more advanced core.

Signed-off-by: Andrzej Puzdrowski <[email protected]>

Author: nvlsianpu

boot/zephyr/main.c

@@ -182,6 +182,7 @@ static void do_boot(struct boot_rsp *rsp)
     __set_MSP(vt->msp);
 #if CONFIG_MCUBOOT_CLEANUP_ARM_CORE
     __set_CONTROL(0x00); /* application will configures core on its own */
+    __ISB();
 #endif
     ((void (*)(void))vt->reset)();
 }