Unlock TLS spinlock on key error in kthread_setspecific.

Thanks to ryancaicse on GitHub for reporting the issue (GitHub Issue #72).

kernel/arch/dreamcast/include/dc/pvr.h

@@ -1440,7 +1440,7 @@ void pvr_mem_stats();
 /* Scene rendering ***************************************************/
 
 /* This API is used to submit triangle strips to the PVR via the TA
-   interace in the chip.
+   interface in the chip.
 
    An important side note about the PVR is that all primitive types
    must be submitted grouped together. If you have 10 polygons for each

kernel/thread/tls.c

@@ -134,6 +134,7 @@ int kthread_setspecific(kthread_key_t key, const void *value) {
     /* Make sure the key is valid. */
     if(key >= next_key || key < 1) {
         errno = EINVAL;
+        spinlock_unlock(&mutex);
         return -1;
     }