nfc: Check hardware before registering the reboot notifer

Nfc driver should not toggle disable pin if nfc hardware isn't present.
Therefore the reboot notifier is only needed if probe is successful and
NFC chip could be enabled while the phone is shutting down.

Change-Id: I4a2e49f1ecb97b20b30845a3e0d9e8929dafbd99
Signed-off-by: Keith Fallows <keithf@codeaurora.org>
Signed-off-by: Houston Hoffman <hhoffman@codeaurora.org>