hwrng: geode - fix return value check in mod_init()

In case of error, the function devm_ioremap() returns NULL pointer
not ERR_PTR(). The IS_ERR() test in the return value check should
be replaced with NULL test.

Fixes: 6e9b5e76882c ("hwrng: geode - Migrate to managed API")
Signed-off-by: Wei Yongjun <[e-mail]>
Signed-off-by: Herbert Xu <[e-mail]>

drivers/char/hw_random/geode-rng.c

···
 				return -ENODEV;
 
 			mem = devm_ioremap(&pdev->dev, rng_base, 0x58);
-			if (IS_ERR(mem))
-				return PTR_ERR(mem);
+			if (!mem)
+				return -ENOMEM;
 			geode_rng.priv = (unsigned long)mem;
 
 			pr_info("AMD Geode RNG detected\n");