logind: add support for TPS65217 Power Button

logind: add support for TPS65217 Power Button

This PMIC is found on TI AM335x based boards like the beaglebone and
beaglebone black.

root@beaglebone-white:~# udevadm info -a /dev/input/event0

Udevadm info starts with the device specified by the devpath and then
walks up the chain of parent devices. It prints for every device
found, all possible attributes in the udev rules key format.
A rule to match, can be composed by the attributes of the device
and the attributes from one single parent device.

  looking at device
'/devices/ocp.3/44e0b000.i2c/i2c-0/0-0024/input/input0/event0':
    KERNEL=="event0"
    SUBSYSTEM=="input"
    DRIVER==""

  looking at parent device
'/devices/ocp.3/44e0b000.i2c/i2c-0/0-0024/input/input0':
    KERNELS=="input0"
    SUBSYSTEMS=="input"
    DRIVERS==""
    ATTRS{name}=="tps65217_pwr_but"
    ATTRS{phys}==""
    ATTRS{uniq}==""
    ATTRS{properties}=="0"

  looking at parent device '/devices/ocp.3/44e0b000.i2c/i2c-0/0-0024':
    KERNELS=="0-0024"
    SUBSYSTEMS=="i2c"
    DRIVERS=="tps65217"
    ATTRS{name}=="tps65217"

  looking at parent device '/devices/ocp.3/44e0b000.i2c/i2c-0':
    KERNELS=="i2c-0"
    SUBSYSTEMS=="i2c"
    DRIVERS==""
    ATTRS{name}=="OMAP I2C adapter"

  looking at parent device '/devices/ocp.3/44e0b000.i2c':
    KERNELS=="44e0b000.i2c"
    SUBSYSTEMS=="platform"
    DRIVERS=="omap_i2c"

  looking at parent device '/devices/ocp.3':
    KERNELS=="ocp.3"
    SUBSYSTEMS=="platform"
    DRIVERS==""