csky: Fixup wrong pt_regs size

The bug is from commit 2054f4af ("csky: bugfix gdb coredump error.")

We change the ELF_NGREG to ELF_NGREG - 2 to fit gdb&gcc define, but forgot
modify ptrace regset.
Now coredump use ELF_NRGEG to parse GPRs and ptrace use pt_regs_regset, so
there are two different reg_sets for userspace.
Signed-off-by: Guo Ren <ren_guo@c-sky.com>

arch/csky/kernel/ptrace.c

@@ -8,6 +8,7 @@
 #include <linux/ptrace.h>
 #include <linux/regset.h>
 #include <linux/sched.h>
+#include <linux/sched/task_stack.h>
 #include <linux/signal.h>
 #include <linux/smp.h>
 #include <linux/uaccess.h>
@@ -159,7 +160,7 @@ static int fpr_set(struct task_struct *target,
 static const struct user_regset csky_regsets[] = {
 	[REGSET_GPR] = {
 		.core_note_type = NT_PRSTATUS,
-		.n = ELF_NGREG,
+		.n = sizeof(struct pt_regs) / sizeof(u32),
 		.size = sizeof(u32),
 		.align = sizeof(u32),
 		.get = &gpr_get,