Revert "squashed update to writeback"

This reverts commit ef55697cb8c44872c0549a24007c6cb6a42fa82c.
Revert "lib/int_sqrt.c: optimize square root algorithm"

This reverts commit f5b05f6315e6bc27eb421ccbe4a6065fa4c4f1cd.
believe shall enhance the deep sleep battery drain fix