soc: mediatek: svs: Fix memory leak in svs_enable_debug_write()

In the Linux kernel, the following vulnerability has been resolved:

soc: mediatek: svs: Fix memory leak in svs_enable_debug_write()

In svs_enable_debug_write(), the buf allocated by memdup_user_nul()

is leaked if kstrtoint() fails.

Fix this by using __free(kfree) to automatically free buf, eliminating

the need for explicit kfree() calls and preventing leaks.

[Angelo: Added missing cleanup.h inclusion]