Revert "ACPI: dock: Don't eval _STA on every show_docked sysfs read"

This reverts commit 1d672ef324e78a467603ef55aa4558cac9f895ba.

Thanks to David Engel <david@istwok.net> for pointing out the problem.
I had not added a previous commit that this patch relied on, causing an
oops whenever the dock sysfs file was read.

Reported-by: David Engel <david@istwok.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>