Delete armv7_sleep which duplicates armv7_cpu_sleep

[john-feith.com]

Summary

armv7_sleep appears to be a duplication of armv7_cpu_sleep.

For consistency with the naming conventions used by the other
implementations kill armv7_sleep and keep armv7_cpu_sleep.

Test Plan

Smoke tested on the ODROID-C1 (Amlogic aml8726-m8b).

[• ian]

I've been meaning to do this for months (I think it was me who introduced the dup).