sandbox: Use memmove() to move overlapping regions

The use of strcpy() to remove characters at the start of a string is safe
in U-Boot, since we know the implementation. But in os.c we are using the
C library's strcpy() function, where this behaviour is not permitted.

Update the code to use memmove() instead.

Reported-by: Coverity (CID: 173279)
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Alexander Graf <agraf@suse.de>
diff --git a/arch/sandbox/cpu/os.c b/arch/sandbox/cpu/os.c
index aa92694..62e05c5 100644
--- a/arch/sandbox/cpu/os.c
+++ b/arch/sandbox/cpu/os.c
@@ -735,9 +735,10 @@
 	}
 
 	/* Look for 'u-boot' in the parent directory of spl/ */
-	p = strstr(fname, "/spl/");
+	p = strstr(fname, "spl/");
 	if (p) {
-		strcpy(p, p + 4);
+		/* Remove the "spl" characters */
+		memmove(p, p + 4, strlen(p + 4) + 1);
 		fd = os_open(fname, O_RDONLY);
 		if (fd >= 0) {
 			close(fd);