Fix compiler warnings: Unused function params

We could use C23's `[[maybe_unused]]` but MSVC doesn't support it.
So we void cast them with an accompanying "unused" comment.

lib/blisp.c

@@ -16,6 +16,8 @@
 static void drain(struct sp_port* port) {
 #if defined(__APPLE__) || defined(__FreeBSD__)
   sp_drain(port);
+#else
+  (void)port; // unused
 #endif
 }
 

lib/chip/blisp_chip_bl60x.c

@@ -6,6 +6,8 @@
 
 int64_t blisp_chip_bl60x_get_eflash_loader(uint8_t clk_type, uint8_t** firmware_buf_ptr)
 {
+  (void)clk_type; // unused
+
   uint8_t* firmware_buf = malloc(sizeof(bl60x_eflash_loader_bin));
   memcpy(firmware_buf, bl60x_eflash_loader_bin, sizeof(bl60x_eflash_loader_bin));
   *(firmware_buf + 0xE0) = 4; // TODO: 40 MHz clock

lib/chip/blisp_chip_bl70x.c

@@ -6,6 +6,8 @@
 
 int64_t blisp_chip_bl70x_get_eflash_loader(uint8_t clk_type, uint8_t** firmware_buf_ptr)
 {
+  (void) clk_type; // ununsed
+
   uint8_t* firmware_buf = malloc(sizeof(bl70x_eflash_loader_bin));
   memcpy(firmware_buf, bl70x_eflash_loader_bin, sizeof(bl70x_eflash_loader_bin));
   *(firmware_buf + 0xE0) = 1; // TODO: 32 MHz clock