alloc_tag: allocate percpu counters for module tags dynamically

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

alloc_tag: allocate percpu counters for module tags dynamically

When a module gets unloaded it checks whether any of its tags are still in

use and if so, we keep the memory containing module's allocation tags

alive until all tags are unused. However percpu counters referenced by

the tags are freed by free_module(). This will lead to UAF if the memory

allocated by a module is accessed after module was unloaded.

To fix this we allocate percpu counters for module allocation tags

dynamically and we keep it alive for tags which are still in use after

module unloading. This also removes the requirement of a larger

PERCPU_MODULE_RESERVE when memory allocation profiling is enabled because

percpu memory for counters does not need to be reserved anymore.