pvr: skip setting up SPM consts buffer when no const shared regs are used
What does this MR do and why?
This skips setting up the SPM consts buffer when no const shared regs are used. This is a temporary measure until the zeroed shaders are replaced with the real ones and is needed to avoid a VK_ERROR_OUT_OF_DEVICE_MEMORY error due to a zero sized allocation.
/cc @CreativeCylon