bootutil: extracted app common library from bootutil_misc

Part of code of boot/bootutil/ is re-implemented in zephyr-rtos
repository.
As some code are defined here and there it becomes problem when
need to include it with outstanding feature in a build.
It is possible to mitigate problem using #fdefry - but this was
rather temporary hack.

This patch introduce new module which is common for MCUBoot build
and application build.
Common code were extracted to bootutil_public.c source file and
bootutil_public.h header

MCUboot also select DISABLE_MCUBOOT_BOOTUTIL_LIB_OWN_LOG Kconfig
option, as it must define log configuration on its own for all its
sourcecode.

Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>
diff --git a/boot/zephyr/CMakeLists.txt b/boot/zephyr/CMakeLists.txt
index 1b6024d..49b0fa0 100644
--- a/boot/zephyr/CMakeLists.txt
+++ b/boot/zephyr/CMakeLists.txt
@@ -113,6 +113,9 @@
   ${BOOT_DIR}/bootutil/src/fault_injection_hardening.c
   )
 
+# library which might be common source code for MCUBoot and an application
+zephyr_link_libraries(MCUBOOT_BOOTUTIL)
+
 if(CONFIG_BOOT_FIH_PROFILE_HIGH)
 zephyr_library_sources(
   ${BOOT_DIR}/bootutil/src/fault_injection_hardening_delay_rng_mbedtls.c