soc: sunxi: sram: Fix probe function ordering issues

Errors from debugfs are intended to be non-fatal, and should not prevent
the driver from probing.

Since debugfs file creation is treated as infallible, move it below the
parts of the probe function that can fail. This prevents an error
elsewhere in the probe function from causing the file to leak. Do the
same for the call to of_platform_populate().

Finally, checkpatch suggests an octal literal for the file permissions.

Fixes: 4af34b57 ("drivers: soc: sunxi: Introduce SoC driver to map SRAMs")
Fixes: 5828729b

 ("soc: sunxi: export a regmap for EMAC clock reg on A64")
Reviewed-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Signed-off-by: Samuel Holland <samuel@sholland.org>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Link: https://lore.kernel.org/r/20220815041248.53268-6-samuel@sholland.org