imx: define functions to configure chip selects in the WEIM

This has the addional effect that the macros CSCR_U, CSCR_L and CSCR_A
are not used anymore in mach-pcm038.c and mach-qong.c.  These still use
the deprecated IO_ADDRESS macro and shouldn't be used in new code.

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: Holger Schurig <hs4233@mail.mn-solutions.de>
Cc: Dmitriy Taychenachev <dimichxp@gmail.com>