ecryptfs: don't reinvent the wheels, please - use struct completion

... and keep the sodding requests on stack - they are small enough.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --cc fs/ecryptfs/ecryptfs_kernel.h
Simple merge

diff --cc fs/ecryptfs/kthread.c
Simple merge

diff --cc fs/ecryptfs/main.c
Simple merge