mmc: fsl_esdhc_imx: fix config check issue when building in SPL

Should use CONFIG_IS_ENABLED not IS_ENABLED for clock and regulator drivers,
CONFIG_IS_ENABLED will check the CONFIG_SPL_CLK and CONFIG_SPL_DM_REGULATOR
when building SPL.

Signed-off-by: Ye Li <ye.li@nxp.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>