ARM: tegra: make debug_ll code build for ARMv6

In a combined ARMv6/v7 kernel, we cannot use the
movt/movw instructions to load an immediate, as they
are not valid on ARMv6.

This changes the file to use an indirect load instead,
as lots of other implementations do.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: linux-tegra@vger.kernel.org