xtensa: drop unused definitions

drop the following unused definitions:
- TS_USEDFPU from arch/xtensa/include/asm/thread_info.h
- current_set from arch/xtensa/kernel/process.c

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

arch/xtensa/kernel/process.c

@@ -52,8 +52,6 @@
 extern void ret_from_fork(void);
 extern void ret_from_kernel_thread(void);
 
-struct task_struct *current_set[NR_CPUS] = {&init_task, };
-
 void (*pm_power_off)(void) = NULL;
 EXPORT_SYMBOL(pm_power_off);