ARM: davinci: remove hawkboard support

This is still a non-generic board.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Acked-by: Sughosh Ganu <urwithsughosh@gmail.com>
Cc: Syed Mohammed Khasim <sm.khasim@gmail.com>
Acked-by: Marek Vasut <marex@denx.de>