greybus: arche-apb-ctrl: Rename init_seq and cleanup fn

apb_ctrl_coldboot_seq() and apb_ctrl_poweroff_seq()
is appropriate name as per spec and implementation, so rename it.
Also move apb_ctrl_poweroff_seq() fn above, to group it with
other _seq functions.

Testing Done: Tested on EVT1.2 and DB3.5 platform.

Signed-off-by: Vaibhav Hiremath <vaibhav.hiremath@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>