drivers: of: add return value to of_reserved_mem_device_init()

Driver calling of_reserved_mem_device_init() might be interested if the
initialization has been successful or not, so add support for returning
error code.

This fixes a build warining caused by commit 7bfa5ab6fa1b ("drivers:
dma-coherent: add initialization from device tree"), which has been
merged without this change and without fixing function return value.

Fixes: 7bfa5ab6fa1b1 ("drivers: dma-coherent: add initialization from device tree")
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Grant Likely <grant.likely@linaro.org>
Cc: Laura Abbott <lauraa@codeaurora.org>
Cc: Josh Cartwright <joshc@codeaurora.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/base/dma-contiguous.c b/drivers/base/dma-contiguous.c
index 473ff48..950fff9 100644
--- a/drivers/base/dma-contiguous.c
+++ b/drivers/base/dma-contiguous.c
@@ -223,9 +223,10 @@
 #undef pr_fmt
 #define pr_fmt(fmt) fmt
 
-static void rmem_cma_device_init(struct reserved_mem *rmem, struct device *dev)
+static int rmem_cma_device_init(struct reserved_mem *rmem, struct device *dev)
 {
 	dev_set_cma_area(dev, rmem->priv);
+	return 0;
 }
 
 static void rmem_cma_device_release(struct reserved_mem *rmem,