Fix issues detected by clang

Logic for delayed memory garbage collection for the case of user space memory will not work as implemented for the case of the kernel build.  That is because the correct context is in place in order to free the user memory when sched_kufree is called, but will not be in place later when the memory garbage collection runs.  If this feature is really needed, then some more substantial redesign is required

SSD1351 driver: add 8-bit parallel interface