x86/mm/pat: Harmonize 'struct memtype *' local variable and function parameter use

We have quite a zoo of 'struct memtype' variable nomenclature:

  new
  entry
  print_entry
  data
  match
  out
  memtype

Beyond the randomness, some of these are outright confusing, especially
when used in larger functions.

Standardize them:

  entry
  entry_new
  entry_old
  entry_print
  entry_match
  entry_out

Signed-off-by: Ingo Molnar <mingo@kernel.org>