Revert "diag : Safeguard for bound checks and integer underflow"

This reverts commit bd379d7c in
which Diag driver is trying to access a variable incorrectly when
reading data from userspace.

Change-Id: I95f1f94ec0f2caf789f969325d343d1052ee9dc8
Signed-off-by: Ravi Aravamudhan <aravamud@codeaurora.org>