arm/imx: remove mx31_setup_weimcs() from mx31.h

The helper function mx31_setup_weimcs() references IOMEM() and
IMX_IO_P2V() but without required header mach/hardware.h included
in mx31.h.  This will break the build of those mx31 based board file
with no direct inclusion of mach/hardware.h, or when indirect inclusion
to mach/hardware.h breaks.

For example, when the inclusion of mach/hardware.h gets removed from
mach/gpio.h, we will see the following compile error.

  CC      arch/arm/mach-imx/mach-pcm037_eet.o
In file included from arch/arm/mach-imx/devices-imx31.h:9:0,
                 from arch/arm/mach-imx/mach-pcm037_eet.c:20:
arch/arm/plat-mxc/include/mach/mx31.h: In function ‘mx31_setup_weimcs’:
arch/arm/plat-mxc/include/mach/mx31.h:129:2: error: implicit declaration of function ‘IOMEM’
arch/arm/plat-mxc/include/mach/mx31.h:129:2: error: implicit declaration of function ‘IMX_IO_P2V’

This patch removes mx31_setup_weimcs() from mx31.h and makes it local
to mach-qong.c, which is the only user for this helper.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>