boot: Add some missing unused arguments
boot: Add some missing unused arguments

In MCUBOOT_RAM_LOAD mode, bootutil_img_hash has some arguments that end
up being unused, which creates warnings.  Add these to the list of
variables intentionally unused.

Signed-off-by: David Brown <0af22db655f3ade5845314d695c1f4910314b0cb@linaro.org>

runtimeco/mcuboot,ATmobica/mcuboot,ATmobica/mcuboot,runtimeco/mcuboot,ATmobica/mcuboot,ATmobica/mcuboot,runtimeco/mcuboot,runtimeco/mcuboot,ATmobica/mcuboot,runtimeco/mcuboot