sandbox: Use the reset driver to handle reset

Move sandbox over to use the reset uclass for reset, instead of a direct
call to do_reset(). This allows us to add tests.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/sandbox/cpu/cpu.c b/arch/sandbox/cpu/cpu.c
index e6ddb17..3a7f5a0 100644
--- a/arch/sandbox/cpu/cpu.c
+++ b/arch/sandbox/cpu/cpu.c
@@ -20,7 +20,7 @@
 unsigned long map_len;
 #endif
 
-void reset_cpu(ulong ignored)
+void sandbox_exit(void)
 {
 	/* Do this here while it still has an effect */
 	os_fd_restore();
@@ -34,13 +34,6 @@
 	os_exit(0);
 }
 
-int do_reset(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
-{
-	reset_cpu(0);
-
-	return 0;
-}
-
 /* delay x useconds */
 void __udelay(unsigned long usec)
 {