libplatsupport: refactor more timers

- The following platforms are changed: am335x,
fvp, hikey, rockpro64
- All platforms pass build
- Except for fvp which doesn't have a machine handy,
the other 3 platforms pass sel4test
- For each platform, the ltimer.c and device-specific
code is more intertwined than I would have liked,
including things like device code branching on
`LTIMER` constants, but I think cleaning the
interface is a project for later

Update hikey dmt driver with more functionality

- dmt_ticks_to_ns
- dmt_is_irq_pending
- dmt_set_timeout_ticks
- dmt_get_ticks

Fix hikey dmt timer initialisation

We would never initialise odd timer id's correctly, instead assigning
them to the previous even timer vaddr.

Fixes for hikey timers

- fix get_time, multiply by NS_IN_S rather than incorrect shift
- convert to and from milliseconds in dmtimer calculations to avoid
accuracy loss
- don't round down, irqs are allowe to come in early

trivial: fix whitespace

Remove pstimer wrappers for hikey

- remove from DMT and refactor DMT into own file
- remove from RTC and refactor RTC into own file
- remove virtual timer implementation (coming back in next commit as
ltimer)