I think there could be at least three different scenarios for 'desert dwarves'.
First, if the dwarves were already formed as a species and had culture and tool use by the time they came to desert, I do not think they would change much. As many other answers here tell, sapient creatures do not adapt to the environment too strongly - they have tools to take the edge off the environmental pressure. Most what would change is the skin and hair color and eye shape.
The second scenario is a scientific 'common ancestor' approach - evolution in your world works pretty much the same as in ours, without magical interference. 'Dwarves' are sapient humanoids evolved from the desert-dwelling burrowing primates. I do not think they would retain all the adaptations of their burrowing ancestors - those were much more adapted to desert. I would say, they would be something like humans, if humans evolved from desert nocturnal stalking omnivores instead of savannah endurance omnivores. Shorter, with more strength and less endurance, possibly big ears, broad and soft feet, and more body fat. I do not know about beards - I'm not up to date on the evolution of human facial hair. Such creatures would since then spread out from their ancestral deserts and live in other environments too.
The third scenario is 'intelligent design' - some magical or scientific power had consciously worked on adapting human or dwarven baseline stock to desert. That power would most likely go overboard and try to create an ideal 'desert-dweller', cramming as many features from different desert animals as possible - here you can just let your imagination run wild. Just take all adaptations from the list here - http://mentalfloss.com/article/57204/20-amazing-animal-adaptations-living-desert.
They would have very variable metabolism, being able to slow it down significantly. A lot of fat, possibly in the form of special humps. Closable nostrils and additional eye memrane like camels, different water exchange as in some dessert antelopes (say, they don't need much water and don't urinate, instead expelling uric acid as solid). These creatures would be actually overspecialized for desert, so it would be hard for them to live in other environments.