proc_sys_permission() is OK in RCU mode

nothing blocking there, since all instances of sysctl
->permissions() method are non-blocking - both of them,
that is.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/proc/proc_sysctl.c

@@ -304,9 +304,6 @@ static int proc_sys_permission(struct inode *inode, int mask,unsigned int flags)
 	struct ctl_table *table;
 	int error;
 
-	if (flags & IPERM_FLAG_RCU)
-		return -ECHILD;
-
 	/* Executable files are not allowed under /proc/sys/ */
 	if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode))
 		return -EACCES;