ARM: bcm: use memory accessors for ioremapped area

The pointer used to pass parameters to an "smc" call is produced
through a call to ioremap().  As such, we should be using functions
like writel() to access it.

Signed-off-by: Alex Elder <elder@linaro.org>
Reviewed-by: Tim Kryger <tim.kryger@linaro.org>
Reviewed-by: Markus Mayer <markus.mayer@linaro.org>
Reviewed-by: Matt Porter <mporter@linaro.org>
Signed-off-by: Matt Porter <mporter@linaro.org>