sandbox: Drop 'const' from sandbox_write()

This function writes to its address so the address should not be declared
as const. Fix it.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/arch/sandbox/cpu/cpu.c b/arch/sandbox/cpu/cpu.c
index 2046cb5..f3af88d 100644
--- a/arch/sandbox/cpu/cpu.c
+++ b/arch/sandbox/cpu/cpu.c
@@ -246,8 +246,7 @@
 	return 0;
 }
 
-void sandbox_write(const void *addr, unsigned int val,
-		   enum sandboxio_size_t size)
+void sandbox_write(void *addr, unsigned int val, enum sandboxio_size_t size)
 {
 	struct sandbox_state *state = state_get_current();