riscv: stacktrace: Move register keyword to beginning of declaration
Using global sp_in_global directly to fix the following warning,
arch/riscv/kernel/stacktrace.c:31:3: warning: ‘register’ is not at beginning of declaration [-Wold-style-declaration]
31 | const register unsigned long current_sp = sp_in_global;
| ^~~~~
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com> Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>