mmc: fsl_esdhc: Add peripheral clock support

The SD clock could be generated by platform clock or peripheral
clock for some platforms. This patch adds peripheral clock
support for T1024/T1040/T2080. To enable it, define
CONFIG_FSL_ESDHC_USE_PERIPHERAL_CLK.

Signed-off-by: Yangbo Lu <yangbo.lu@freescale.com>
Cc: York Sun <yorksun@freescale.com>
Cc: Pantelis Antoniou <panto@antoniou-consulting.com>
Reviewed-by: York Sun <yorksun@freescale.com>