s390/zcore: copy vector registers into the image data

The /sys/kernel/debug/zcore/mem interface delivers the memory of the
old system with the CPU registers stored to the assigned locations in
each prefix page.

For the vector registers the prefix page of each CPU has an address of
a 1024 byte save area at 0x11b0. But the /sys/kernel/debug/zcore/mem
interface fails copy the vector registers saved at boot of the zfcpdump
kernel into the dump image.

Copy the saved vector registers of a CPU to the outout buffer if the
memory area that is read via /sys/kernel/debug/zcore/mem intersects
with the vector register save area of this CPU.

Acked-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>