arm64/common: Critical Section Optimization.

Replace critical_section with spinlock.
The benefits of doing this are:

1. It makes the code logic clearer, with different resources protected by different locks.

2. It improves system responsiveness and avoids contention issues caused by acquiring the same large lock.

Signed-off-by: wangzhi16 <wangzhi16@xiaomi.com>

arch/arm64/src/common/arm64_fork.c

@@ -60,16 +60,10 @@
 
 void arm64_fork_fpureg_save(struct fork_s *context)
 {
-  irqstate_t flags;
-
   /* Take a snapshot of the thread fpu reg context right now */
 
-  flags = enter_critical_section();
-
   arm64_fpu_save(context->fpu);
   UP_DSB();
-
-  leave_critical_section(flags);
 }
 
 #endif