gpu: ion: fix sparse non static symbol warnings

Fixes the following sparse warnings:

drivers/staging/android/ion/tegra/tegra_ion.c:23:19: warning:
 symbol 'idev' was not declared. Should it be static?
drivers/staging/android/ion/tegra/tegra_ion.c:24:19: warning:
 symbol 'tegra_user_mapper' was not declared. Should it be static?
drivers/staging/android/ion/tegra/tegra_ion.c:25:5: warning:
 symbol 'num_heaps' was not declared. Should it be static?
drivers/staging/android/ion/tegra/tegra_ion.c:26:17: warning:
 symbol 'heaps' was not declared. Should it be static?
drivers/staging/android/ion/tegra/tegra_ion.c:28:5: warning:
 symbol 'tegra_ion_probe' was not declared. Should it be static?
drivers/staging/android/ion/tegra/tegra_ion.c:66:5: warning:
 symbol 'tegra_ion_remove' was not declared. Should it be static?
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/android/ion/tegra/tegra_ion.c

@@ -20,12 +20,11 @@
 #include "../ion.h"
 #include "../ion_priv.h"
 
-struct ion_device *idev;
-struct ion_mapper *tegra_user_mapper;
-int num_heaps;
-struct ion_heap **heaps;
+static struct ion_device *idev;
+static int num_heaps;
+static struct ion_heap **heaps;
 
-int tegra_ion_probe(struct platform_device *pdev)
+static int tegra_ion_probe(struct platform_device *pdev)
 {
 	struct ion_platform_data *pdata = pdev->dev.platform_data;
 	int err;
@@ -63,7 +62,7 @@ int tegra_ion_probe(struct platform_device *pdev)
 	return err;
 }
 
-int tegra_ion_remove(struct platform_device *pdev)
+static int tegra_ion_remove(struct platform_device *pdev)
 {
 	struct ion_device *idev = platform_get_drvdata(pdev);
 	int i;