[PATCH net-next] net: stmmac: fix stmmac_simple_pm_ops build errors

["Russell King (Oracle)" <rmk+kernel@armlinux.org.uk>]

The kernel test robot reports that various drivers have an undefined
reference to stmmac_simple_pm_ops. This is caused by
EXPORT_SYMBOL_GPL_SIMPLE_DEV_PM_OPS() defining the struct as static
and omitting the export when CONFIG_PM=n, unlike DEFINE_SIMPLE_PM_OPS()
which still defines the struct non-static.

Switch to using DEFINE_SIMPLE_PM_OPS() + EXPORT_SYMBOL_GPL(), which
means we always define stmmac_simple_pm_ops, and it will always be
visible for dwmac-* to reference whether modular or built-in.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202508132051.a7hJXkrd-lkp@intel.com/
Closes: https://lore.kernel.org/oe-kbuild-all/202508132158.dEwQdick-lkp@intel.com/
Closes: https://lore.kernel.org/oe-kbuild-all/202508140029.V6tDuUxc-lkp@intel.com/
Closes: https://lore.kernel.org/oe-kbuild-all/202508161406.RwQuZBkA-lkp@intel.com/
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index a55e43804670..fa3d26c28502 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -8024,8 +8024,9 @@ int stmmac_resume(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(stmmac_resume);
 
-EXPORT_GPL_SIMPLE_DEV_PM_OPS(stmmac_simple_pm_ops, stmmac_suspend,
-			     stmmac_resume);
+/* This is not the same as EXPORT_GPL_SIMPLE_DEV_PM_OPS() when CONFIG_PM=n */
+DEFINE_SIMPLE_DEV_PM_OPS(stmmac_simple_pm_ops, stmmac_suspend, stmmac_resume);
+EXPORT_SYMBOL_GPL(stmmac_simple_pm_ops);
 
 #ifndef MODULE
 static int __init stmmac_cmdline_opt(char *str)
-- 
2.30.2