build: separate preprocessing from DTB compilation

This is a small change to separate preprocessing of device tree sources
into their own build step as opposed to combining them. The impact of
this is more on separation of concerns than anything tangible, but it's
helpful to avoid doing more than necessary in a build rule.

Change-Id: I770291bd9d9f627c93e82556a40f753bf27eef93
Signed-off-by: Chris Kay <chris.kay@arm.com>
1 file changed