arm/tegra: remove unused defines

PPI_NR is never used in arch/arm/mach-tegra/irq.c. Remove it.

Signed-off-by: Peter De Schrijver <pdeschrijver@nvidia.com>
Acked-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Olof Johansson <olof@lixom.net>