sw: wip commit -- getting dfu working

Now that we have SPI and USB both working, we can start to close the
loop and get DFU working.

Signed-off-by: Sean Cross <sean@xobs.io>

sw/src/spi-gpio.c

@@ -0,0 +1,27 @@
+#include <stdio.h>
+#include <generated/csr.h>
+
+#include "spi-gpio.h"
+
+static uint8_t do_mirror;
+static uint8_t oe_mirror;
+
+void gpioSetMode(int pin, int mode) {
+    if (mode)
+        oe_mirror |= 1 << pin;
+    else
+        oe_mirror &= ~(1 << pin);
+    picospi_oe_write(oe_mirror);
+}
+
+void gpioWrite(int pin, int val) {
+    if (val)
+        do_mirror |= 1 << pin;
+    else
+        do_mirror &= ~(1 << pin);
+    picospi_do_write(do_mirror);
+}
+
+int gpioRead(int pin) {
+    return !!(picospi_di_read() & (1 << pin));
+}