nvmem: meson-efuse: Fix return value of nvmem callbacks

Read/write callbacks registered with nvmem core expect 0 to be returned
on success and a negative value to be returned on failure.

meson_efuse_read() and meson_efuse_write() call into
meson_sm_call_read() and meson_sm_call_write() respectively which return
the number of bytes read or written on success as per their api
description.

Fix to return error if meson_sm_call_read()/meson_sm_call_write()
returns an error else return 0.

Fixes: a29a63b ("nvmem: meson-efuse: simplify read callback")
Cc: stable@vger.kernel.org
Signed-off-by: Joy Chakraborty <joychakr@google.com>
Reviewed-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20240628113704.13742-3-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Joy Chakraborty

drivers/nvmem/meson-efuse.c

@@ -18,18 +18,24 @@ static int meson_efuse_read(void *context, unsigned int offset,
 			    void *val, size_t bytes)
 {
 	struct meson_sm_firmware *fw = context;
+	int ret;
 
-	return meson_sm_call_read(fw, (u8 *)val, bytes, SM_EFUSE_READ, offset,
-				  bytes, 0, 0, 0);
+	ret = meson_sm_call_read(fw, (u8 *)val, bytes, SM_EFUSE_READ, offset,
+				 bytes, 0, 0, 0);
+
+	return ret < 0 ? ret : 0;
 }
 
 static int meson_efuse_write(void *context, unsigned int offset,
 			     void *val, size_t bytes)
 {
 	struct meson_sm_firmware *fw = context;
+	int ret;
+
+	ret = meson_sm_call_write(fw, (u8 *)val, bytes, SM_EFUSE_WRITE, offset,
+				  bytes, 0, 0, 0);
 
-	return meson_sm_call_write(fw, (u8 *)val, bytes, SM_EFUSE_WRITE, offset,
-				   bytes, 0, 0, 0);
+	return ret < 0 ? ret : 0;
 }
 
 static const struct of_device_id meson_efuse_match[] = {