linux-wandboard

um: get rid of sysdep/sc.h

only sysdep/sigcontext.h uses it and very few definitions are
actually used.  The rest refers to symbols that don't even
exist anymore anyway.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Richard Weinberger <richard@nod.at>