boards.cfg: keep it sorted filling the board field

The boards.cfg file has allowed to use "-" for the board (= 6th) field
if the board name is the same as the 7th field.

But I notice one problem.
Because tools/reformat.py sorts the lines in the simple alphabetical
order (= the order of character code), some entries for the same board
are not lined up together.

For example, "bf527-ezkit" and "bf527-ezkit-v2" share the same board.
But they are located separately because "bf527-ezkit" fills the board
field with "-" whereas "bf527-ezkit-v2" specifies it explicitely.

The similar things can be seen:
 - between "trizepsive" and "polaris"
 - between "RRvision" and "RRvision_LCD"
 - between "korat" and "korat_perm"
 - between "lwmon5" and "lcd4_lwmon5"

This commit was generated by the following command:

awk '$6 == "-" { $6 = $7 } { print }' boards.cfg \
  | tools/reformat.py -i -d '-' -s 8  > boards0.cfg; \
  mv boards0.cfg boards.cfg

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>