panic_handle: Add a debugfs entry to disable/enable emmc ipanic manually

panic_handle: Add a debugfs entry to disable/enable emmc ipanic manually

BZ: 17477

emmc ipanic feature would dump the task kernel stacks of all processes.
That erases all the log_buf usually. Although emmc ipanic writes the info
to storage, but it's not good for living debugging using ITP or other
debug tools. We want to check sys log and other info such like
specific variables and memory, when the panic happens.

This patch adds disable_emmc_ipanic, a new debugfs entry. To disable
emmc ipanic manually:

The patch also adds a boot parameter disable_emmc_ipanic which can be used
when kernel panic at booting.

By default, disable_emmc_ipanic==0.

Change-Id: I2642d2a28a1e6838fb65bc4811b701fe87bdd6ae
Signed-off-by: Yanmin Zhang <yanmin.zhang@intel.com>
Reviewed-on: http://android.intel.com:8080/26995
Reviewed-by: Guerard, Christophe <christophe.guerard@intel.com>
Tested-by: Zhang, Dongxing <dongxing.zhang@intel.com>
Reviewed-by: buildbot <buildbot@intel.com>
Tested-by: buildbot <buildbot@intel.com>