Revert "Revmoed file from fpga zbbl which should not have been added."

This reverts commit d6944cdaa4.

fpga/zsbl/bios.S

@@ -0,0 +1,102 @@
+#include "system.h"
+
+PERIOD = (SYSTEMCLOCK / 2)
+
+.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, (EXT_MEM_END - 8)
+
+	li a0, 0x00000000
+	li a1, EXT_MEM_BASE
+	#li a2, 128*1024*1024/512 # copy 128MB
+	li a2, 127*1024*1024/512 # copy 127MB upper 1MB contains the return address (ra)
+	#li a2, 800 # copy 400KB
+	jal ra, copyFlash
+	
+	fence.i
+	# now toggle led so we know the copy completed.
+
+	# write to gpio
+	li	t2, 0xFF
+	la	t3, 0x1006000C
+	li	t4, 5
+
+loop:
+
+	# delay
+	li	t0, PERIOD/2
+delay1:	
+	addi	t0, t0, -1
+	bge	t0, x0, delay1
+	sw	t2, 0x0(t3)
+
+	li	t0, PERIOD/2
+delay2:	
+	addi	t0, t0, -1
+	bge	t0, x0, delay2
+	sw	x0, 0x0(t3)
+
+	addi	t4, t4, -1
+	bgt	t4, x0, loop
+
+
+	# now that the card is copied and the led toggled we
+	# jump to the copied contents of the sd card.
+
+jumpToLinux:	
+	csrrs	a0, 0xF14, x0   # copy hart ID to a0
+	li	a1, FDT_ADDRESS  # This is the device tree address
+	la	a2, end_of_bios
+	li	t0, EXT_MEM_BASE  # start of code
+	
+	jalr	x0, t0, 0
+
+end_of_bios:	
+
+	
+
+