ST7701: Raise DMA priority.

This seems to work nicely with WiFi as of the upstream Pico SDK fix:

raspberrypi/pico-sdk#2209

Author: Gadgetoid

drivers/st7701/st7701.cpp

@@ -333,6 +333,7 @@ void ST7701::start_frame_xfer()
         // Regular RGB565 framebuffer
         dma_channel_config config = dma_channel_get_default_config(st_dma);
         channel_config_set_transfer_data_size(&config, DMA_SIZE_32);
+        channel_config_set_high_priority(&config, true);
         channel_config_set_dreq(&config, pio_get_dreq(st_pio, parallel_sm, true));
         channel_config_set_bswap(&config, true);
         channel_config_set_chain_to(&config, st_dma2);
@@ -342,6 +343,7 @@ void ST7701::start_frame_xfer()
         channel_config_set_transfer_data_size(&config, DMA_SIZE_32);
         channel_config_set_read_increment(&config, false);
         dma_channel_configure(st_dma2, &config, &dma_hw->ch[st_dma].al3_read_addr_trig, &next_line_addr, 1, false);
+        hw_set_bits(&bus_ctrl_hw->priority, (BUSCTRL_BUS_PRIORITY_PROC1_BITS | BUSCTRL_BUS_PRIORITY_DMA_R_BITS | BUSCTRL_BUS_PRIORITY_DMA_W_BITS));
       }
       else {
         st_dma3 = dma_claim_unused_channel(true);