arm64: tegra: Adjust length of CCPLEX cluster MMIO region

[ Upstream commit 2b14cbd643feea5fc17c6e8bead4e71088c69acd ]

The Tegra186 CCPLEX cluster register region is 4 MiB is length, not 4
MiB - 1. This was likely presumed to be the "limit" rather than length.
Fix it up.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>