make: image: Attach the MODEL_SUFFIX to the model string passed to build_image.

The suffix can be set to whatever the caller of the makefile wants to append
to the model. For ChromeOS, this would be the ChromeOS version number. For
Fuchsia this will currently be nothing, but could become something meaningful
in the future.

Change-Id: Ib6e0964fd6ce7b11e386a667b22647b91890e8f7
1 file changed