defconfig: 8916: disable debug and etm save and restore support

Current configuration to save and restore debug and etm registers
are not applicable for ARMv8 targets which has a different
implementation for saving and restoring these registers. Disable this
default configuration.

Change-Id: I10e1a6e99a899bb74495a7caac8afae568f382f4
Signed-off-by: Aparna Das <adas@codeaurora.org>