defconfig: Change panic timeout for target sm8150

Change panic timeout for target sm8150 so that the device
reboots immediately when a kernel panic is encountered,
instead of waiting for 5 seconds.

Change-Id: I6d883920e04aac1085109979391532157e63078f
Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>