Patch moves large temporary u64 W[80] from stack to ctx struct:

* reduces stack usage by 640 bytes
* saves one 640-byte memset() per sha512_transform()
  (we still do it after *all* iterations are done)
* quite unexpectedly saves 1.6k of code on i386
  because stack offsets now fit into 8bits
  and many stack addressing insns got 3 bytes smaller:

# size sha512.o.org sha512.o
text       data     bss     dec     hex filename
8281        372       0    8653    21cd sha512.o.org
6649        372       0    7021    1b6d sha512.o

# objdump -d sha512.o.org | cut -b9- >sha512.d.org
# objdump -d sha512.o | cut -b9- >sha512.d
# diff -u sha512.d.org sha512.d
[snip]
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>