Currently each i.MX processor has its own function for displaying the silicon
revision.

Introduce a generic function for this purpose, so that all i.MX processors can
reuse it.
Signed-off-by: NFabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: NJason Liu <jason.hui@linaro.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: NSascha Hauer <s.hauer@pengutronix.de>

We had hardcoded cpu_is_ macros for mxc architectures till now. As we
want to run the same kernel on i.MX31 and i.MX35 this patch adds cpu_is_
macros which expand to 0 or 1 if only one architecture is compiled in and
only check for the cpu type if more than one architecture is compiled
in.
Signed-off-by: NSascha Hauer <s.hauer@pengutronix.de>