greybus: power_supply: remove references to kernel header

In Greybus power supply macro definitions we have a comment that point
to a kernel header, remove it since we have a specification for that.

As at it, align the status values to the upper values.

Signed-off-by: Rui Miguel Silva <rui.silva@linaro.org>
Reviewed-by: Sandeep Patil <sspatil@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>