implement proper i2c controller and power button

[Coto]

otherwise they cause lockups on TWL ARM7 cores when any GPIO port is used, like the TWL volume buttons

[Coto]

implemented proper i2c irq handler, fixes ARM7 crashes when pressing volume up / down, and performs reset/shutdown properly by power button events https://bitbucket.org/Coto88/toolchaingenericds/commits/9b57fef15260b1dff286763198c0271947605a58

https://bitbucket.org/Coto88/toolchaingenericds-multiboot/commits/1fb8ee95ebb1ada53a11c799c411a9719cfd063a

https://bitbucket.org/Coto88/snemulds/commits/7b8d089e9403002cd65bd2448aaf6db7f140be3b