[PATCH 1/7] x86: Add mtrr_{add,del}_wc_if_needed

These MTRR helpers add a WC MTRR if PAT is disabled. Modern drivers should be using ioremap_wc, etc. to get WC memory; the MTRR is just a fallback if the system doesn't have PAT. So, rather than allocating an unnecessary MTRR even on PAT systems and having error handling spread out and handled

[PATCH 1/7] x86: Add mtrr_{add,del}_wc_if_needed

These MTRR helpers add a WC MTRR if PAT is disabled. Modern drivers should be using ioremap_wc, etc. to get WC memory; the MTRR is just a fallback if the system doesn't have PAT. So, rather than allocating an unnecessary MTRR even on PAT systems and having error handling spread out and handled