Minimal spinlock API based on the existing atomic.h layer. Usage
works just like irq_lock(), but takes an argument to a specific struct
k_spinlock_t to un/lock. No attempt at implementing fairness or
backoff semantics. No attempt made at architecture-specific assembly.
When CONFIG_SMP is not enabled, this code falls back to a zero-size
struct and becomes functionally identical to irq_lock/unlock().
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
Andy Ross