ahci power management

[Matthew Dillon]

:I have updated the patch at 
:http://leaf.dragonflybsd.org/~hofmann/ahci_pwrmgmt.patch
:accordingly.
:Link power management can now be switched on and off with a sysctl.
:On my system it is "hw.ahci0.0.link_pwr_mgmt"
:(0 = disabled, 1 = medium, 2 = aggressive).
:
:Thanks for the help on the ML and on irc,
:  Johannes

    This is looking very good.  Just one more thing and I can commit it
    for this release.  The AHCI driver can be unloaded... the sysctl
    nodes have to be destroyed when it is.  It can be done in
    ahci_port_free().  Keep in mind that the function can be called
    on a partially initialized port so conditionalize the destruction of
    the sysctl node on it having been installed.

					-Matt
					Matthew Dillon 
					<dillon at backplane.com>