ecryptfs: inode.c mmap.c use unaligned byteorder helpers

Fixe sparse warnings:
fs/ecryptfs/inode.c:368:15: warning: cast to restricted __be64
fs/ecryptfs/mmap.c:385:12: warning: incorrect type in assignment (different base types)
fs/ecryptfs/mmap.c:385:12:    expected unsigned long long [unsigned] [assigned] [usertype] file_size
fs/ecryptfs/mmap.c:385:12:    got restricted __be64 [usertype] <noident>
fs/ecryptfs/mmap.c:428:12: warning: incorrect type in assignment (different base types)
fs/ecryptfs/mmap.c:428:12:    expected unsigned long long [unsigned] [assigned] [usertype] file_size
fs/ecryptfs/mmap.c:428:12:    got restricted __be64 [usertype] <noident>

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Cc: Michael Halcrow <mhalcrow@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>