fix warning/Werror in NO_FLASH build

src/rp2_common/hardware_flash/flash.c

@@ -112,6 +112,7 @@ void __no_inline_not_in_flash_func(flash_range_program)(uint32_t flash_offs, con
 //-----------------------------------------------------------------------------
 // Lower-level flash access functions
 
+#if !PICO_NO_FLASH
 // Bitbanging the chip select using IO overrides, in case RAM-resident IRQs
 // are still running, and the FIFO bottoms out. (the bootrom does the same)
 static void flash_cs_force(bool high) {
@@ -159,6 +160,7 @@ static void __no_inline_not_in_flash_func(flash_do_cmd)(const uint8_t *txbuf, ui
     flash_flush_cache();
     flash_enable_xip_via_boot2();
 }
+#endif
 
 // Use standard RUID command to get a unique identifier for the flash (and
 // hence the board)