ARM: tegra: don't unlock MMIO access to DBGLAR

There is no need to unlock MMIO access to the DBGLAR all the time. Doing
so may even cause problems if a SW bug causes writes to that MMIO region.

Cortex-A15 processors do not support the CP14 register write the code
currently uses to unlock the DBGLAR; the instruction throws an undefined
instruction exceptions. This prevents tegra_secondary_startup() from
executing on Tegra114, and hence prevents SMP.

Remove the code that unlocks this access.

Signed-off-by: Joseph Lo <josephl@nvidia.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>