mediatek: mt7622: enable HW RNG

MT7622 provides are hardware RNG with upstream Linux driver. Enable
compilation of this driver to make use of the hardware RNG.

Signed-off-by: David Bauer <mail@david-bauer.net>

target/linux/mediatek/mt7622/config-5.10

@@ -206,6 +206,8 @@ CONFIG_HAS_DMA=y
 CONFIG_HAS_IOMEM=y
 CONFIG_HAS_IOPORT_MAP=y
 CONFIG_HOLES_IN_ZONE=y
+CONFIG_HW_RANDOM=y
+CONFIG_HW_RANDOM_MTK=y
 CONFIG_I2C=y
 CONFIG_I2C_BOARDINFO=y
 CONFIG_I2C_CHARDEV=y