printk: Fix signed integer overflow when defining LOG_BUF_LEN_MAX

In the Linux kernel, the following vulnerability has been resolved: printk: Fix signed integer overflow when defining LOG_BUF_LEN_MAX Shifting 1 << 31 on a 32-bit int causes signed integer overflow, which leads to undefined behavior. To prevent this, cast 1 to u32 before performing the shift, ensuring well-defined behavior. This change explicitly avoids any potential overflow by ensuring that the shift occurs on an unsigned 32-bit integer.