In order to avoid duplicate symbols with legacy PWM API implementations,
the new PWM framework needs to conflict with any of the existing legacy
implementations. This is done in two ways: for implementations provided
by drivers, a conflict is added to the driver to ensure it will have to
be ported to the PWM subsystem before it can coexist with other PWM
providers. For architecture-specific code, the conflict is added to the
PWM symbol to avoid confusion when a previously picked platform or
machine can no longer be selected because of the PWM subsystem being
included.
Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>