* use valid_params_if macro for lock assertion
* fixup param checking in pwm.h
* Fix range of fractional divider parameter check in pwm.h
Co-authored-by: Luke Wren <wren6991@gmail.com>
In C, func() is a function taking an unspecified number of arguments,
vs func(void) a function taking no arguments. In C++ both forms indicate
"no arguments."
Update these headers to use the (void) form, which is correct in both
languages and avoids complaints when -Wstrict-prototypes is specified.
