eCryptfs: Remove ecryptfs_header_cache_2

Now that ecryptfs_lookup_interpose() is no longer using
ecryptfs_header_cache_2 to read in metadata, the kmem_cache can be
removed and the ecryptfs_header_cache_1 kmem_cache can be renamed to
ecryptfs_header_cache.

Signed-off-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>

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

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

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