staging: lustre: ptlrpc: kfree used instead of kvfree

staging: lustre: ptlrpc: kfree used instead of kvfree

rq_reqbuf is allocated using kvmalloc() but released in one occasion
using kfree() instead of kvfree().

The issue was found using grep based on a similar bug.

Fixes: d7e09d0397e8 ("add Lustre file system client support")
Fixes: ee0ec1946ec2 ("lustre: ptlrpc: Replace uses of OBD_{ALLOC,FREE}_LARGE")
Cc: Peng Tao <bergwolf@gmail.com>
Cc: Oleg Drokin <oleg.drokin@intel.com>
Cc: James Simmons <jsimmons@infradead.org>
Signed-off-by: Nadav Amit <namit@vmware.com>
Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>