zephyr: restore removed #endif in target.h
zephyr: restore removed #endif in target.h

8accafd5c7e8d19c832574993ffb664f69fa345e has removed #endif statement
belonging to unrelated #if, causing compilation error. Restore it.

Signed-off-by: Sergey Koziakov <1188c0871940f22968eebcd5db13219bbb32e811@gmail.com>

ATmobica/mcuboot,tamban01/mcuboot,utzig/mcuboot,ATmobica/mcuboot,utzig/mcuboot,runtimeco/mcuboot,ATmobica/mcuboot,runtimeco/mcuboot,ATmobica/mcuboot,runtimeco/mcuboot,tamban01/mcuboot,utzig/mcuboot,runtimeco/mcuboot,utzig/mcuboot,tamban01/mcuboot,tamban01/mcuboot,utzig/mcuboot,ATmobica/mcuboot,tamban01/mcuboot,runtimeco/mcuboot