Build latexpdf and html targets by default
Build latexpdf and html targets by default

I rarely want to build 'help', but I always want latexpdf! Change the
default build target to latexpdf and html

Signed-off-by: Grant Likely <9069e6f5a2b566e2674a0ba1e2bf39c12c195fad@arm.com>

devicetree-org/devicetree-specification