diag: Mode reset command has to be handled on APPS proc

Mode reset command is handled by APPS proc. If the apps process
has not registered with diag for handling the mode reset command,
diag has to send error response code back. This patch fixes
that issue.

Change-Id: Id4d99f0e909fa3a78e8682825984a99042021bad
Signed-off-by: Katish Paran <kparan@codeaurora.org>