ARM: mx3: fix build failure concerning MXC_INT_MMC_SDHC2

Commit c0745129 (imx-esdhc: update devices registration) renamed
MX35_INT_MMC_SDHC2 to MX35_INT_ESDHC2 which broke expansion of the
MXC_INT_MMC_SDHC2 macro.
As  (the only user of MXC_INT_MMC_SDHC2) is only used on
mx31 use the MX31 prefixed symbol to define its resources.  Moreover to
reduce further confusion mxcsdhc_device0 is fixed accordingly and the MXC
prefixed symbols are removed.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>