drivers: dma: rpi_pico: Correct handling of NULL filter_param

From the API documentation, `dma_api_chan_filter`` can be given a value
of NULL for `filter_param`. Match the behaviour of most implementations,
and return true. This removes misleading error messages logged during
tests (e.g. `test_tst_dma0_m2m_loop`).

Signed-off-by: Andrew Featherstone <[email protected]>

Author: ajf58

drivers/dma/dma_rpi_pico.c

@@ -288,8 +288,7 @@ static bool dma_rpi_pico_api_chan_filter(const struct device *dev, int ch, void
 	uint32_t filter;
 
 	if (!filter_param) {
-		LOG_ERR("filter_param must not be NULL");
-		return false;
+		return true;
 	}
 
 	filter = *((uint32_t *)filter_param);