soc: aspeed: Add NULL check in aspeed_lpc_enable_snoop()

In the Linux kernel, the following vulnerability has been resolved: soc: aspeed: Add NULL check in aspeed_lpc_enable_snoop() devm_kasprintf() returns NULL when memory allocation fails. Currently, aspeed_lpc_enable_snoop() does not check for this case, which results in a NULL pointer dereference. Add NULL check after devm_kasprintf() to prevent this issue. [arj: Fix Fixes: tag to use subject from 3772e5da4454]