ARM: tegra: fix multiple asm/hardware/gic.h inclusion

arch/arm/mach-tegra/board-dt-tegra20.c: included 'asm/hardware/gic.h'
twice remove the duplicates.

Signed-off-by: Danny Kukawka <danny.kukawka@bisect.de>
[swarren: rewrote commit subject]
Signed-off-by: Stephen Warren <swarren@nvidia.com>