Address issues found in specification

Remove cond_t type from COND_IF and WHILE_LOOP, they aren't used
anywhere else in the description of these operators

Clean up the types for VARIABLE ops
  VARIABLE and VARIABLE_WRITE change var_t to in_t which represents
    the real types
  VARIABLE_READ changes var_t to out_t for the same reason

Switch the order of index_t and in_out_t to make the Supported Data
Type table consistent between SCATTER and GATHER.

Fix a few typos

Signed-off-by: Eric Kunze <eric.kunze@arm.com>
Change-Id: I76295d6783b7531562cd730a12f189508579eeb2