board-blackbay: changed fuel gauge gpio pin name to max_fg_alert

board-blackbay: changed fuel gauge gpio pin name to max_fg_alert

BZ: 31370

This patch modifies the gpio pin name to max_fg_alert. This will
avoid the dependency to know device id as the alert pin is present
on all platforms we can have single unique gpio pin name.

Change-Id: Ic7234e8e743e79c9286e685cb5b2ee49d382bc40
Signed-off-by: Ramakrishna Pallala <ramakrishna.pallala@intel.com>
Reviewed-on: http://android.intel.com:8080/42788
Reviewed-by: Tc, Jenny <jenny.tc@intel.com>
Reviewed-by: Hari, NeelamX <neelamx.hari@intel.com>
Reviewed-by: Lebouc, Christophe <christophe.lebouc@intel.com>
Tested-by: Lebouc, Christophe <christophe.lebouc@intel.com>
Reviewed-by: buildbot <buildbot@intel.com>
Tested-by: buildbot <buildbot@intel.com>