ARM: tegra: delete gpio-names.h

gpio-names.h defines IDs for GPIOs. This information now comes from
device tree, so delete this stale header. The one remaining use-case is
board-paz00.c's wifi_rfkill device. Isolate the knowledge of those GPIO
IDs into that file. Let's hope the values stay valid:-)

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