LoongArch64: Add 'bt' command support

- Add basic support for the 'bt' command.
- LooongArch64: Add 'bt -f' command support
- LoongArch64: Add 'bt -l' command support

E.g. With this patch:
crash> bt
PID: 1832     TASK: 900000009a552100  CPU: 11   COMMAND: "bash"
 #0 [900000009beffb60] __cpu_possible_mask at 90000000014168f0
 crash-utility#1 [900000009beffb60] __crash_kexec at 90000000002e7660
 crash-utility#2 [900000009beffcd0] panic at 9000000000f0ec28
 crash-utility#3 [900000009beffd60] sysrq_handle_crash at 9000000000a2c188
 crash-utility#4 [900000009beffd70] __handle_sysrq at 9000000000a2c85c
 crash-utility#5 [900000009beffdc0] write_sysrq_trigger at 9000000000a2ce10
 crash-utility#6 [900000009beffde0] proc_reg_write at 90000000004ce454
 crash-utility#7 [900000009beffe00] vfs_write at 900000000043e838
 crash-utility#8 [900000009beffe40] ksys_write at 900000000043eb58
 crash-utility#9 [900000009beffe80] do_syscall at 9000000000f2da54
 crash-utility#10 [900000009beffea0] handle_syscall at 9000000000221440
crash>
...

Co-developed-by: Youling Tang <[email protected]>
Signed-off-by: Youling Tang <[email protected]>
Signed-off-by: Ming Wang <[email protected]>

defs.h

@@ -2234,6 +2234,8 @@ struct offset_table {                    /* stash of commonly-used offsets */
 	long irq_data_irq;
 	long zspage_huge;
 	long zram_comp_algs;
+	long task_struct_thread_reg01;
+	long task_struct_thread_reg03;
 };
 
 struct size_table {         /* stash of commonly-used sizes */