Revert "mm: Disable UKSM by default"

This reverts commit 978c61eb279c4d3353e62ad5ac82a7414dcfe96d.
Revert "mm: Add UKSM 0.1.2.2"

This reverts commit 15f2f21a3c1f28b2af8b7b836e0cf37de12b3e20.
Revert "defconfigs: Enable UKSM"

This reverts commit 42c13e079e43cf4fc9b3b49a1edfde60298cf6da.