pm2301-charger: Die temp thermal protection

This patch adds support for die temperature thermal protection
in pm2301 driver.

Signed-off-by: Rupesh Kumar <rupesh.kumar@stericsson.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Reviewed-by: Hakan BERG <hakan.berg@stericsson.com>
Reviewed-by: Philippe LANGLAIS <philippe.langlais@stericsson.com>