[PATCH] s390: use __cpcmd in vmcp_write

vmcp_write uses GPF_DMA for the memory allocation of the response buffer, so
it can use the low level function __cpcmd directly, no need to call the
wrapper.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>