usb: mtu3: constify struct debugfs_reg32

mtu3_prb_regs is never changed and can therefore be made const.

This allows the compiler to put it in the text section instead of the
data section.

Before:
   text    data     bss     dec     hex filename
  19966    7120       0   27086    69ce drivers/usb/mtu3/mtu3_debugfs.o

After:
   text    data     bss     dec     hex filename
  20142    6992       0   27134    69fe drivers/usb/mtu3/mtu3_debugfs.o
Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>

drivers/usb/mtu3/mtu3_debugfs.c

@@ -276,7 +276,7 @@ static const struct file_operations mtu3_ep_fops = {
 	.release = single_release,
 };
 
-static struct debugfs_reg32 mtu3_prb_regs[] = {
+static const struct debugfs_reg32 mtu3_prb_regs[] = {
 	dump_prb_reg("enable", U3D_SSUSB_PRB_CTRL0),
 	dump_prb_reg("byte-sell", U3D_SSUSB_PRB_CTRL1),
 	dump_prb_reg("byte-selh", U3D_SSUSB_PRB_CTRL2),
@@ -349,7 +349,7 @@ static const struct file_operations mtu3_probe_fops = {
 static void mtu3_debugfs_create_prb_files(struct mtu3 *mtu)
 {
 	struct ssusb_mtk *ssusb = mtu->ssusb;
-	struct debugfs_reg32 *regs;
+	const struct debugfs_reg32 *regs;
 	struct dentry *dir_prb;
 	int i;