Remove sysctl.h from fs.h

Rrrr, addition of sysctl.h to fs.h was't very smart, because simple
editing of the former will buy you big recompile, where it shouldn't
have to.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>