[S390] vmur: allocate single record buffers instead of one big data buffer

vmur allocates one contiguous kernel buffer to copy user data when creating
ccw programs for punch or printer. If big block sizes are used, under memory
pressure it can happen, that we do not get memory in one chunk. Now we
allocate memory for each single record to avoid high order allocations.

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