hwrng: omap - write registers after enabling the clock

Commit 383212425c ("hwrng: omap - Add device variant for SafeXcel
IP-76 found in Armada 8K") added support for the SafeXcel IP-76 variant
of the IP. This modification included getting a reference and enabling a
clock. Unfortunately, this was done *after* writing to the
RNG_INTMASK_REG register. This generally works fine when the driver is
built-in because the clock might have been left enabled by the
bootloader, but fails short when the driver is built as a module: it
causes a system hang because a register is being accessed while the
clock is not enabled.

This commit fixes that by making the register access *after* enabling
the clock.

This issue was found by the kernelci.org testing effort.

Fixes: 383212425c ("hwrng: omap - Add device variant for SafeXcel IP-76 found in Armada 8K")
Cc: <stable@vger.kernel.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/char/hw_random/omap-rng.c

@@ -397,7 +397,6 @@ static int of_get_omap_rng_device_details(struct omap_rng_dev *priv,
 				irq, err);
 			return err;
 		}
-		omap_rng_write(priv, RNG_INTMASK_REG, RNG_SHUTDOWN_OFLO_MASK);
 
 		priv->clk = of_clk_get(pdev->dev.of_node, 0);
 		if (IS_ERR(priv->clk) && PTR_ERR(priv->clk) == -EPROBE_DEFER)
@@ -408,6 +407,8 @@ static int of_get_omap_rng_device_details(struct omap_rng_dev *priv,
 				dev_err(&pdev->dev, "unable to enable the clk, "
 						    "err = %d\n", err);
 		}
+
+		omap_rng_write(priv, RNG_INTMASK_REG, RNG_SHUTDOWN_OFLO_MASK);
 	}
 	return 0;
 }