mmc: fsl_esdhc: Fix wp_enable issue

The wp-gpios property is used for gpio, if this is set, the WP pin is muxed
to gpio function, can't be used as internal WP checking. However the codes
remain to use internal WP checking.

This patch changes to examine the "fsl,wp-controller" for enabling internal WP
checking, and "wp-gpios" for muxing to gpio.

Signed-off-by: Ye Li <ye.li@nxp.com>