board: sama5d2_xplained: change SDHCI GCK's clock source to UPLL

Change the clock source of the SDHCI's generated clock from PLLA to
UPLL clock to align to Linux driver.

Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>
Reviewed-by: Andreas Bießmann <andreas@biessmann.org>

board/atmel/sama5d2_xplained/sama5d2_xplained.c

@@ -175,7 +175,7 @@ static void board_sdhci0_hw_init(void)
 
 	at91_periph_clk_enable(ATMEL_ID_SDMMC0);
 	at91_enable_periph_generated_clk(ATMEL_ID_SDMMC0,
-					 GCK_CSS_PLLA_CLK, 1);
+					 GCK_CSS_UPLL_CLK, 1);
 }
 
 static void board_sdhci1_hw_init(void)
@@ -191,7 +191,7 @@ static void board_sdhci1_hw_init(void)
 
 	at91_periph_clk_enable(ATMEL_ID_SDMMC1);
 	at91_enable_periph_generated_clk(ATMEL_ID_SDMMC1,
-					 GCK_CSS_PLLA_CLK, 1);
+					 GCK_CSS_UPLL_CLK, 1);
 }
 
 int board_mmc_init(bd_t *bis)