arm: mediatek: select arch timer for mt7629

arm: mediatek: select arch timer for mt7629

This chip has an armv7 arch timer according to the dts. Select it in
Kconfig to enforce the support for it.
Otherwise the system time is just completely wrong if user forget to
enable ARM_ARCH_TIMER in kernel config.

Fixes: a43379dddf1b ("arm: mediatek: add MT7629 smp bring up code")
Signed-off-by: Chuanhong Guo <gch981213@gmail.com>
Link: https://lore.kernel.org/r/20220409091347.2473449-1-gch981213@gmail.com
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>