debug: add parameters to prevent entering debug mode on errors

On non-developer devices kgdb prevents CONFIG_PANIC_TIMEOUT from
rebooting the device after a panic. Add module parameters
debug_core.break_on_exception and debug_core.break_on_panic to
allow skipping debug on panics and exceptions respectively.  Both
default to true to preserve existing behavior.

Change-Id: I75dce7263e96cee069a9750920cce83dc6f98e8c
Signed-off-by: Colin Cross <ccross@android.com>