net: designware: Make driver independent from DM_GPIO again

Commit 90b7fc924adf "net: designware: support phy reset device-tree
bindings" made DW GMAC driver dependent on DM_GPIO by unconditional
usage of purely DM_GPIO stuff like:
 * dm_gpio_XXX()
 * gpio_request_by_name()

But since that driver as of today might be easily used without
DM_GPIO (that's the case for Synopsys AXS10x boards) we're
shielding all DM_GPIO things by ifdefs.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Beniamino Galvani <b.galvani@gmail.com>
Cc: Joe Hershberger <joe.hershberger@ni.com>
Cc: Sjoerd Simons <sjoerd.simons@collabora.co.uk>
Cc: Sonic Zhang <sonic.zhang@analog.com>
Cc: Bin Meng <bmeng.cn@gmail.com>
Cc: Marek Vasut <marex@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
diff --git a/drivers/net/designware.h b/drivers/net/designware.h
index 51ba769..d345c5b 100644
--- a/drivers/net/designware.h
+++ b/drivers/net/designware.h
@@ -8,7 +8,9 @@
 #ifndef _DW_ETH_H
 #define _DW_ETH_H
 
-#include <asm/gpio.h>
+#ifdef CONFIG_DM_GPIO
+#include <asm-generic/gpio.h>
+#endif
 
 #define CONFIG_TX_DESCR_NUM	16
 #define CONFIG_RX_DESCR_NUM	16
@@ -234,7 +236,10 @@
 #ifndef CONFIG_DM_ETH
 	struct eth_device *dev;
 #endif
+#ifdef CONFIG_DM_GPIO
 	struct gpio_desc reset_gpio;
+#endif
+
 	struct phy_device *phydev;
 	struct mii_dev *bus;
 };