zephyr: io: include 'bootutil_log.h' and declare log module membership

This fixes below error when building with 'MCUBOOT_INDICATION_LED' and
'LOG' enabled:

  In file included from zephyr/include/zephyr/logging/log.h:11,
                   from zephyr/include/zephyr/usb/usb_device.h:43,
                   from bootloader/mcuboot/boot/zephyr/io.c:26:
  mcuboot/boot/zephyr/io.c: In function 'io_led_init':
  zephyr/include/zephyr/logging/log_core.h:151:20: error:
    '__log_level' undeclared (first use in this function)
    151 |         (_level <= __log_level) &&                                          \
        |                    ^~~~~~~~~~~

Fixes: 433b8480 ("zephyr: Move IO functions out of main to separate file")
Signed-off-by: Piotr Dymacz <pepe2k@gmail.com>