Fix PTE_ADDR to account for NX bit
Fix PTE_ADDR to account for NX bit

NX is the only high bit in a PTE, and we previously only masked out
the low bits.

aclements/sv6,bowlofstew/sv6,bowlofstew/sv6,aclements/sv6,bowlofstew/sv6,aclements/sv6,aclements/sv6,aclements/sv6,bowlofstew/sv6,bowlofstew/sv6