arm64: Revert "mm: provide idmap pointer to cpu_replace_ttbr1()"

arm64: Revert "mm: provide idmap pointer to cpu_replace_ttbr1()"

This reverts commit 1682c45b920643c, which is no longer needed now that
we create the permanent kernel mapping directly during early boot.

This is a RINO (revert in name only) given that some of the code has
moved around, but the changes are straight-forward.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20240214122845.2033971-69-ardb+git@google.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>