arm64: Clear the initial ID map correctly before remapping

In the attempt to clear and recreate the initial ID map for LPA2, we
wrongly use 'start - end' as the map size and make the memset() almost a
nop.

Fix it by passing the correct map size.

Fixes: 9684ec18 ("arm64: Enable LPA2 at boot if supported by the system")
Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20240621092809.162-1-yuzenghui@huawei.com


Signed-off-by: Will Deacon <will@kernel.org>