media: vpss: fix a potential NULL pointer dereference

In case ioremap fails, the fix returns -ENOMEM to avoid NULL
pointer dereference.
Signed-off-by: Kangjie Lu <kjlu@umn.edu>
Acked-by: Lad, Prabhakar <prabhakar.csengg@gmail.com>
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/platform/davinci/vpss.c

@@ -518,6 +518,11 @@ static int __init vpss_init(void)
 		return -EBUSY;
 
 	oper_cfg.vpss_regs_base2 = ioremap(VPSS_CLK_CTRL, 4);
+	if (unlikely(!oper_cfg.vpss_regs_base2)) {
+		release_mem_region(VPSS_CLK_CTRL, 4);
+		return -ENOMEM;
+	}
+
 	writel(VPSS_CLK_CTRL_VENCCLKEN |
 		     VPSS_CLK_CTRL_DACCLKEN, oper_cfg.vpss_regs_base2);