mx25pdk: Set the eSDHC PER clock to 48 MHz

The maximum SD clock frequency in High Speed mode is 50 MHz. This change
makes it possible to get 48 MHz from the USB PLL (240 MHz / 5 / 1)
instead of the previous 33.25 MHz from the AHB clock (133 MHz / 2 / 2).

Signed-off-by: Benoît Thébaudeau <benoit@wsystem.com>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>

board/freescale/mx25pdk/mx25pdk.c

@@ -175,6 +175,12 @@ int board_mmc_init(bd_t *bis)
 
 	imx_iomux_v3_setup_multiple_pads(sdhc1_pads, ARRAY_SIZE(sdhc1_pads));
 
+	/*
+	 * Set the eSDHC1 PER clock to the maximum frequency lower than or equal
+	 * to 50 MHz that can be obtained, which requires to use UPLL as the
+	 * clock source. This actually gives 48 MHz.
+	 */
+	imx_set_perclk(MXC_ESDHC1_CLK, true, 50000000);
 	esdhc_cfg[0].sdhc_clk = mxc_get_clock(MXC_ESDHC1_CLK);
 	return fsl_esdhc_initialize(bis, &esdhc_cfg[0]);
 }