pwm: lpc32xx: correct number of PWM channels from 2 to 1

pwm: lpc32xx: correct number of PWM channels from 2 to 1

LPC32xx SoC has two independent PWM controllers, they have different
clock parents, clock gates and even slightly different controls, and
each of these two PWM controllers has one output channel. Due to
almost similar controls arranged in a row it is incorrectly set that
there is one PWM controller with two channels, fix this problem, which
at the moment prevents separate configuration of different clock
parents and gates for both PWM controllers.

The change makes previous PWM device node description incompatible
with this update.

Signed-off-by: Vladimir Zapolskiy <vz@mleia.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>