net: broadcom: fix a mistake about ioremap resource

Commit d7a5502b0b ("net: broadcom: convert to
devm_platform_ioremap_resource_byname()") will broke this driver.
idm_base and nicpm_base were optional, after this change, they are
mandatory. it will probe fails with -22 when the dtb doesn't have them
defined. so revert part of this commit and make idm_base and nicpm_base
as optional.

Fixes: d7a5502b0b ("net: broadcom: convert to devm_platform_ioremap_resource_byname()")
Reported-by: Jonathan Richardson <jonathan.richardson@broadcom.com>
Cc: Scott Branden <scott.branden@broadcom.com>
Cc: Ray Jui <ray.jui@broadcom.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Dejin Zheng <zhengdejin5@gmail.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/bgmac-platform.c

@@ -172,6 +172,7 @@ static int bgmac_probe(struct platform_device *pdev)
 {
 	struct device_node *np = pdev->dev.of_node;
 	struct bgmac *bgmac;
+	struct resource *regs;
 	const u8 *mac_addr;
 
 	bgmac = bgmac_alloc(&pdev->dev);
@@ -206,16 +207,21 @@ static int bgmac_probe(struct platform_device *pdev)
 	if (IS_ERR(bgmac->plat.base))
 		return PTR_ERR(bgmac->plat.base);
 
-	bgmac->plat.idm_base =
+	regs = platform_get_resource_byname(pdev, IORESOURCE_MEM, "idm_base");
-		devm_platform_ioremap_resource_byname(pdev, "idm_base");
+	if (regs) {
+		bgmac->plat.idm_base = devm_ioremap_resource(&pdev->dev, regs);
 		if (IS_ERR(bgmac->plat.idm_base))
 			return PTR_ERR(bgmac->plat.idm_base);
 		bgmac->feature_flags &= ~BGMAC_FEAT_IDM_MASK;
+	}
 
-	bgmac->plat.nicpm_base =
+	regs = platform_get_resource_byname(pdev, IORESOURCE_MEM, "nicpm_base");
-		devm_platform_ioremap_resource_byname(pdev, "nicpm_base");
+	if (regs) {
+		bgmac->plat.nicpm_base = devm_ioremap_resource(&pdev->dev,
+							       regs);
 		if (IS_ERR(bgmac->plat.nicpm_base))
 			return PTR_ERR(bgmac->plat.nicpm_base);
+	}
 
 	bgmac->read = platform_bgmac_read;
 	bgmac->write = platform_bgmac_write;