drivers: nvadsp: fix sparse warnings

Fix following sparse warnings by including header dev-t21x.h, which
has function declarations, in dev-t21x.c.

dev-t21x.c:284:5: warning: symbol 'nvadsp_pm_t21x_init' was not declared.
Should it be static?
dev-t21x.c:296:5: warning: symbol 'nvadsp_reset_t21x_init' was not declared.
Should it be static?

Bug 200299572

Change-Id: I5f16da0852ab9083fba7395cfbd66ec012014663
Signed-off-by: Nitin Kumbhar <nkumbhar@nvidia.com>
Reviewed-on: http://git-master/r/1474440
Signed-off-by: Nitin Kumbhar <nkumbhar@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/1537325
Reviewed-by: svccoveritychecker <svccoveritychecker@nvidia.com>
GVS: Gerrit_Virtual_Submit
Reviewed-by: Amit Sharma (SW-TEGRA) <amisharma@nvidia.com>

drivers/platform/tegra/nvadsp/dev-t21x.c

@@ -25,6 +25,7 @@
 
 #include "dev.h"
 #include "amc.h"
+#include "dev-t21x.h"
 
 #ifdef CONFIG_PM
 static void nvadsp_clocks_disable(struct platform_device *pdev)