assert: show stacks with the sp from regs

1. Get the value of sp from dump regs when an exception occurs,
   to avoid getting the value of fp from up_getsp and causing
   incomplete stack printing.
2. Determine which stack the value belongs to based on the value
   of SP to avoid false reports of stack overflow

Signed-off-by: zhangyuan21 <zhangyuan21@xiaomi.com>

arch/sparc/src/sparc_v8/sparc_v8_registerdump.c

@@ -41,9 +41,10 @@
  * Name: up_getusrsp
  ****************************************************************************/
 
-uintptr_t up_getusrsp(void)
+uintptr_t up_getusrsp(void *regs)
 {
-  return CURRENT_REGS[REG_I6];
+  uint32_t *ptr = regs;
+  return ptr[REG_I6];
 }
 
 /****************************************************************************