uboot-imx

configs: imx: Make CONFIG_SYS_PROMPT uniform across FSL boards

There is no real benefit in adding the board name into U-boot's prompt.

Use the simple "=> " prompt across FSL boards.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Otavio Salvador <otavio@ossystems.com.br>