PM: Documentation/power/states.txt: fix repetition

inconvenience, this method requires minimal work by the kernel, since

the firmware will also handle restoring memory contents on resume. 

For suspend-to-disk, a mechanism called swsusp called 'swsusp' (Swap

Suspend) is used to write memory contents to free swap space.

swsusp has some restrictive requirements, but should work in most

cases. Some, albeit outdated, documentation can be found in

Documentation/power/swsusp.txt. Alternatively, userspace can do most

of the actual suspend to disk work, see userland-swsusp.txt.

For suspend-to-disk, a mechanism called 'swsusp' (Swap Suspend) is used

to write memory contents to free swap space. swsusp has some restrictive

requirements, but should work in most cases. Some, albeit outdated,

documentation can be found in Documentation/power/swsusp.txt.

Alternatively, userspace can do most of the actual suspend to disk work,

see userland-swsusp.txt.

Once memory state is written to disk, the system may either enter a

low-power state (like ACPI S4), or it may simply power down. Powering