tegra: Use const for pinmux_config_pingroup/table()

These two functions don't actually modify their arguments so add a const
keyword.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Tom Warren <twarren@nvidia.com>
diff --git a/arch/arm/cpu/tegra20-common/pinmux.c b/arch/arm/cpu/tegra20-common/pinmux.c
index 08b8305..a2a0916 100644
--- a/arch/arm/cpu/tegra20-common/pinmux.c
+++ b/arch/arm/cpu/tegra20-common/pinmux.c
@@ -554,7 +554,7 @@
 	writel(reg, muxctl);
 }
 
-void pinmux_config_pingroup(struct pingroup_config *config)
+void pinmux_config_pingroup(const struct pingroup_config *config)
 {
 	enum pmux_pingrp pin = config->pingroup;
 
@@ -563,7 +563,7 @@
 	pinmux_set_tristate(pin, config->tristate);
 }
 
-void pinmux_config_table(struct pingroup_config *config, int len)
+void pinmux_config_table(const struct pingroup_config *config, int len)
 {
 	int i;