esoc: mdm: Remove power off step from debug mode

After debug is done, a complete power down of the modem
will wipe out the crash cause information.
Remove the power down step and rely on a reset during the
subsequent power up.

Change-Id: Ic3157d5a8d22f7b16a6ecc1fa325d2127d8aafca
Signed-off-by: Hanumant Singh <hanumant@codeaurora.org>