Define _NPCM and the last PC_FREEn constant in terms of _NPCPV.

[jhb]

Summary

This applies one of the changes from
5567d6b4419b02a2099527228b1a51cc55a5b47d to other architectures
besides arm64.

Sponsored by: DARPA

[kib]

Do you plan to extract the definitions into some common file?

[jhb]

No, I had not planned on using a common file. Mostly I just felt this is clearer to the reader about how these values are defined. I will look to see if some sort of <sys/pventry_common.h> or the like might make sense.