ncpfs: fix a braino in OOM handling in ncp_fill_cache()

Failing to allocate an inode for child means that cache for *parent* is
incompletely populated.  So it's parent directory inode ('dir') that
needs NCPI_DIR_CACHE flag removed, *not* the child inode ('inode', which
is what we'd failed to allocate in the first place).

Fucked-up-in: commit 5e993e25 ("ncpfs: get rid of d_validate() nonsense")
Fucked-up-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: stable@vger.kernel.org # v3.19
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>