arm64: Rename top-level directory

As a finishing touch, align the top-level arch directory name with the
kernel's naming scheme.

Acked-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20250404165233.3205127-9-oliver.upton@linux.dev
Signed-off-by: Will Deacon <will@kernel.org>
25 files changed