uboot-imx

mx6slevk: Remove get_board_rev()

get_board_rev() just returns the cpu revision, which does not make it really
useful for distinguishing between revisions of the board.

Let's get rid of get_board_rev() as it is not being used with its correct
meaning.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>