x86: drop {,reg16_}inoutportreg variables

x86: drop {,reg16_}inoutportreg variables

The checking against reg16_inoutportreg can be had with a simple test of
a bit, and the value setting from inoutportreg can be replaced by using
the actual register's reg_type field.

Note that the so far redundant 2nd instance of OPERAND_TYPE_INOUTPORTREG
is left in place, for its use in type_names[].