memory: tegra30-mc: Fix IRQ handler.

In Tegra30 any memory controller interrupt would cause an infinite loop in the
IRQ handler. Additionally, a garbage pointer was used to read the MC
status registers, which causes wrong values to be printed if a MC error
occurred.

Signed-off-by: Tuomas Tynkkynen <ttynkkynen@nvidia.com>
Reviewed-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>