Consolidate PTRACE_DETACH

Identical handlers of PTRACE_DETACH go into ptrace_request().
Not touching compat code.
Not touching archs that don't call ptrace_request.

Signed-off-by: Alexey Dobriyan <adobriyan@sw.ru>
Acked-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/um/kernel/ptrace.c

@@ -119,11 +119,6 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data)
 		break;
 	}
 
-	case PTRACE_DETACH:
-		/* detach a process that was attached. */
-		ret = ptrace_detach(child, data);
- 		break;
-
 #ifdef PTRACE_GETREGS
 	case PTRACE_GETREGS: { /* Get all gp regs from the child. */
 		if (!access_ok(VERIFY_WRITE, p, MAX_REG_OFFSET)) {