fpga: stratix10-soc: Fix return value check in s10_ops_write_init()

In case of error, the function stratix10_svc_allocate_memory()
returns ERR_PTR() and never returns NULL. The NULL test in the
return value check should be replaced with IS_ERR().

Fixes: e7eef1d7 ("fpga: add intel stratix10 soc fpga manager driver")
Signed-off-by: NZheng Yongjun <zhengyongjun3@huawei.com>
Reviewed-by: NRuss Weight <russell.h.weight@intel.com>
Cc: stable@vger.kernel.org
Acked-by: NXu Yilun <yilun.xu@intel.com>
Link: https://lore.kernel.org/r/20221126071430.19540-1-zhengyongjun3@huawei.comSigned-off-by: NXu Yilun <yilun.xu@intel.com>

drivers/fpga/stratix10-soc.c

@@ -213,9 +213,9 @@ static int s10_ops_write_init(struct fpga_manager *mgr,
 	/* Allocate buffers from the service layer's pool. */
 	for (i = 0; i < NUM_SVC_BUFS; i++) {
 		kbuf = stratix10_svc_allocate_memory(priv->chan, SVC_BUF_SIZE);
-		if (!kbuf) {
+		if (IS_ERR(kbuf)) {
 			s10_free_buffers(mgr);
-			ret = -ENOMEM;
+			ret = PTR_ERR(kbuf);
 			goto init_done;
 		}