ARM: Tegra: Harmony: Fix conflicting GPIO numbering

Currently, both the WM8903 and TPS6586x chips attempt to register with
gpiolib using the same GPIO numbers. This causes the audio driver to
fail to initialize.

To solve this, add a define to board-harmony.h for the TPS6586x, and make
board-harmony-power.c use this define, instead of directly referencing
TEGRA_NR_GPIOS.

This fixes a regression introduced by commit
6f168f2f.
ARM: tegra: harmony: initialize the TPS65862 PMIC

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Colin Cross <ccross@android.com>