tpm: use idr_find(), not idr_find_slowpath()

idr_find_slowpath() is not intended to be part of the public API, it's
an implementation detail.  There's no reason to skip straight to the
slowpath here.

Link: http://lkml.kernel.org/r/1480369871-5271-64-git-send-email-mawilcox@linuxonhyperv.com
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Tested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Peter Huewe <peterhuewe@gmx.de>
Cc: Marcel Selhorst <tpmdd@selhorst.net>
Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>