ANDROID: sdcardfs: Propagate dentry down to inode_change_ok()

ANDROID: sdcardfs: Propagate dentry down to inode_change_ok()

Since commit 31051c85b5e2 ("fs: Give dentry to inode_change_ok()
instead of inode"), to avoid clearing of capabilities or security
related extended attributes too early, inode_change_ok() will
need to take dentry instead of inode. Propagate it down to
sdcardfs_setattr() and also rename it to setattr_prepare(),
otherwise we run into following build error:

  CC [M]  fs/sdcardfs/inode.o
fs/sdcardfs/inode.c: In function ‘sdcardfs_setattr’:
fs/sdcardfs/inode.c:644:8: error: implicit declaration of function ‘inode_change_ok’ [-Werror=implicit-function-declaration]
  err = inode_change_ok(inode, ia);
        ^

Change-Id: I714b4f4f68b7fea1ac82a71d2f323c76b11fa008
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>