Port changes from PATCHv2 of Memory allocation profiling patchset

This fixes the feature on 32 bit architectures.

Official changelog:
- Simplified allocation tagging macros;
- Runtime enable/disable sysctl switch (/proc/sys/vm/mem_profiling)
  instead of kernel command-line option;
- CONFIG_MEM_ALLOC_PROFILING_BY_DEFAULT to select default enable state;
- Changed the user-facing API from debugfs to procfs (/proc/allocinfo);
- Removed context capture support to make patch incremental;
- Renamed uninstrumented allocation functions to use _noprof suffix;
- Added __GFP_LAST_BIT to make the code cleaner;
- Removed lazy per-cpu counters; it turned out the memory savings was
  minimal and not worth the performance impact;

Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>