staging/lustre/llite: avoid nonatomic memory alloc under spinlock

ll_intent_drop_lock() may sleep in memory allocation, which
should not be called inside spinlock.

Signed-off-by: Lai Siyao <lai.siyao@intel.com>
Signed-off-by: Jian Yu <jian.yu@intel.com>
Reviewed-on: http://review.whamcloud.com/10674
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-2272


Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>