board: freescale: p1_p2_rdb_pc: Do not set MPC85xx_PMUXCR_SDHC_WP bit when SDHC_WP...

board: freescale: p1_p2_rdb_pc: Do not set MPC85xx_PMUXCR_SDHC_WP bit when SDHC_WP is used as GPIO

When MPC85xx_PMUXCR_SDHC_WP is set then SDHC controller automatically makes
inserted SD card readonly if GPIO[9] is active.

In some design GPIO[9] pin does not have to be connected to SD card
write-protect pin and can be used as GPIO.

So do not set MPC85xx_PMUXCR_SDHC_WP bit when GPIO[9] is not used for
SDHC_WP functionality.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>