Remove C tests

The previous tests are not useful anymore.

sw/tests/test_main.c

@@ -1,29 +1,7 @@
 #include <stdio.h>
-#include <stdint.h>
-
-#include <spi.h>
-
-uint16_t retval;
 
 int main(void)
 {
-    printf("Setting SPI location to 0x02\n");
-    *(uint8_t*)0x7ff0 = 2;
-    if (!(*(uint8_t*)0x7ff0 == 2)) {
-        printf("Expected 0x02 at 0x7ff0\n");
-        return 1;
-    }
-    printf("Done!\n\n");
-
-    printf("Starting spi_byte test...\n");
-    retval = spi_byte(0xa5);
-    if (retval != 0) {
-        printf("Expected 0 return value from spi_byte\n");
-        return 1;
-    }
-    printf("Done!   %x\n\n", retval);
-
-    printf("Starting spi_deselect test...\n");
-    spi_deselect();
+    printf("No test to run!\n");
     return 0;
 }