ARM: tegra: fix the status of PWM DT nodes

We should be defining the PWM nodes with status as "disabled" in the
chip-specific dtsi file, since we don't know whether specific boards
will use the PWM or not. This patch fixes the PWM node status for
Tegra20 and Tegra30.

Also fixed the one user of PWM, which is the Tegra20 medcom-wide board,
so that PWM is set to "okay" in the board-specific dts file.

Signed-off-by: Andrew Chew <achew@nvidia.com>
[swarren: in medcom-wide: fixed node sort order, removed duplicate pwm:
label, fixed syntax error]
Signed-off-by: Stephen Warren <swarren@nvidia.com>