Fix HWPMC module on armv6/armv7

[arnaud.ysmal_stormshield.eu]

Summary

On armv[67] hwpmc as a module cannot be loaded as the file hwpmc_armv7.c is not included (link_elf: symbol pmc_armv7_finalize undefined error message).

This also fix the armv[67] INVARIANT build.

[arnaud.ysmal_stormshield.eu]

Already commited.