layers: Fix CmdUpdateBuffer API definition
layers: Fix CmdUpdateBuffer API definition

Change-Id: I7a8a2215ceb3523ca74534fe547600bb585223a7

KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers