configs: at91: sam9x60: Add required configs for the USB clock

Add the configs required to use the SAM9X60's USB clock.

Signed-off-by: Sergiu Moga <sergiu.moga@microchip.com>
Reviewed-by: Claudiu Beznea <claudiu.beznea@microchip.com>
[claudiu.beznea: added CONFIG_AT91_SAM9X60_USB to
 sam9x60_curiosity_mmc1_defconfig]
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
diff --git a/configs/sam9x60ek_mmc_defconfig b/configs/sam9x60ek_mmc_defconfig
index 2caeacc..b0307ec 100644
--- a/configs/sam9x60ek_mmc_defconfig
+++ b/configs/sam9x60ek_mmc_defconfig
@@ -59,6 +59,7 @@
 CONFIG_CLK_AT91=y
 CONFIG_AT91_GENERIC_CLK=y
 CONFIG_AT91_SAM9X60_PLL=y
+CONFIG_AT91_SAM9X60_USB=y
 CONFIG_CPU=y
 CONFIG_AT91_GPIO=y
 CONFIG_DM_I2C=y