alpha: don't bother passing switch_stack separately from regs

It's needed only in setup_sigcontext() and it's always reg - <constant>;
no point passing it all way down through the call chain.  This is just
the signal.c side of that stuff; next will come the asm glue one...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
1 file changed