imx: rename Kconfig symbol for "LogicPD MX27 LITEKIT platform"

Not using MACH_IMX27LITE makes machine_is_imx27lite always return 0
independent of building support for this machine.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Cc: Sascha Hauer <kernel@pengutronix.de>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Daniel Schaeffer <daniel.schaeffer@timesys.com>