Added start.s to spitest directory.

tests/custom/spitest/spitest.c

@@ -92,7 +92,7 @@ void main() {
   do {
     // Send 8 dummy bytes (fifo should be empty)
     for (j = 0; j < 8; j++) {
-      spi_sendbyte(0xaa);
+      spi_sendbyte(0xaa + j);
     }
     
     // Reset counter. Process bytes AS THEY COME IN.

tests/custom/spitest/start.s

@@ -0,0 +1,59 @@
+.section .init
+.global _start
+.type _start, @function
+
+_start:
+	  # Initialize global pointer
+	.option push
+	.option norelax
+	1:auipc gp, %pcrel_hi(__global_pointer$)
+	addi  gp, gp, %pcrel_lo(1b)
+	.option pop
+	
+	li x1, 0
+	li x2, 0
+	li x4, 0
+	li x5, 0
+	li x6, 0
+	li x7, 0
+	li x8, 0
+	li x9, 0
+	li x10, 0
+	li x11, 0
+	li x12, 0
+	li x13, 0
+	li x14, 0
+	li x15, 0
+	li x16, 0
+	li x17, 0
+	li x18, 0
+	li x19, 0
+	li x20, 0
+	li x21, 0
+	li x22, 0
+	li x23, 0
+	li x24, 0
+	li x25, 0
+	li x26, 0
+	li x27, 0
+	li x28, 0
+	li x29, 0
+	li x30, 0
+	li x31, 0
+
+
+
+	# set the stack pointer to the top of memory - 8 bytes (pointer size)
+	li sp, 0x87FFFFF8
+
+	jal ra, main
+	jal ra, _halt
+
+.section .text
+.global _halt
+.type _halt, @function
+_halt:
+	li gp, 1
+	li a0, 0
+	ecall
+	j _halt