nvmem: fix nvmem_cell_get_from_lookup()

We check if the pointer returned by __nvmem_device_get() is not NULL
while we should actually check if it is not IS_ERR(nvmem). Fix it.

While we're at it: fix the next error path where we should assign an
error value to cell before returning.
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Acked-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/nvmem/core.c

@@ -953,9 +953,9 @@ nvmem_cell_get_from_lookup(struct device *dev, const char *con_id)
 		    (strcmp(lookup->con_id, con_id) == 0)) {
 			/* This is the right entry. */
 			nvmem = __nvmem_device_get(NULL, lookup->nvmem_name);
-			if (!nvmem) {
+			if (IS_ERR(nvmem)) {
 				/* Provider may not be registered yet. */
-				cell = ERR_PTR(-EPROBE_DEFER);
+				cell = ERR_CAST(nvmem);
 				goto out;
 			}
 
@@ -963,6 +963,7 @@ nvmem_cell_get_from_lookup(struct device *dev, const char *con_id)
 						       lookup->cell_name);
 			if (!cell) {
 				__nvmem_device_put(nvmem);
+				cell = ERR_PTR(-ENOENT);
 				goto out;
 			}
 		}