sandbox: swap_case: Use statics where possible

Some functions and a struct should be marked static since they are not
used outside this file. Update them.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/drivers/misc/swap_case.c b/drivers/misc/swap_case.c
index eb32d10..8abf88a 100644
--- a/drivers/misc/swap_case.c
+++ b/drivers/misc/swap_case.c
@@ -286,8 +286,8 @@
 	}
 }
 
-int sandbox_swap_case_read_io(struct udevice *dev, unsigned int addr,
-			      ulong *valuep, enum pci_size_t size)
+static int sandbox_swap_case_read_io(struct udevice *dev, unsigned int addr,
+				     ulong *valuep, enum pci_size_t size)
 {
 	struct swap_case_priv *priv = dev_get_priv(dev);
 	unsigned int offset;
@@ -304,8 +304,8 @@
 	return 0;
 }
 
-int sandbox_swap_case_write_io(struct udevice *dev, unsigned int addr,
-			       ulong value, enum pci_size_t size)
+static int sandbox_swap_case_write_io(struct udevice *dev, unsigned int addr,
+				      ulong value, enum pci_size_t size)
 {
 	struct swap_case_priv *priv = dev_get_priv(dev);
 	unsigned int offset;
@@ -392,7 +392,7 @@
 	return 0;
 }
 
-struct dm_pci_emul_ops sandbox_swap_case_emul_ops = {
+static struct dm_pci_emul_ops sandbox_swap_case_emul_ops = {
 	.get_devfn = sandbox_swap_case_get_devfn,
 	.read_config = sandbox_swap_case_read_config,
 	.write_config = sandbox_swap_case_write_config,