You can use the command line to make and download the image. It is same as Make Target parameters, add a make at the beginning.
make snip.scan-BCM943362WCD4 download run
Is there a make target command that only dowloads the image, not build and dowload the image?
The formal way to do it is just to issue make twice with download target, the first call to make, will build the applications and download the code. After that all the subsequent calls to make, will just do downloading, because the binaries are all built. So in theory next makes are just download commands.
The other way, is to issue an openOCD command manually. you can find a sample of those commands in tools/makefiles/standard_platform_targets.mk, you can have a look at the download_bootloader target for example (here is a sample):
$(call CONV_SLASHES,$(OPENOCD_FULL_NAME)) -f $(OPENOCD_PATH)$(JTAG).cfg -f $(OPENOCD_PATH)$(HOST_OPENOCD).cfg -f $(OPENOCD_PATH)$(HOST_OPENOCD)-flash-app.cfg -c "flash write_image erase $(BOOTLOADER_OUTFILE).stripped.elf" -c "shutdown"
offcourse a lot of these are in Make variable to account for different make targets, but the idea is to issue a "flash write_image erase xxx.stripped.elf" following by shutdown command. For more details have a look at OpenOCD command line options.
Also note that the actual make download is downloading 3 programs: Bootloader, DCT and Application, so if you are going to do downloading manually, you need to repeat the previous step 3 times (one for each stripped image). There is currently ongoing work to produce a combined imaged that can be used to write the 3 images at once, but it won't be released until next version.