trivial: Style changed files

nvidia: Del. get_nth_irq/pmem & related functions

Now that the hard-coded addresses and IRQ numbers are being removed,
these functions are no longer necessary.

nvidia: Move timer HW management to driver level

Instead of allocating and managing all resources in the ltimer level,
this commit refactors the related code and moves them into the driver
level. This moves the responsibilities down into a more suitable
abstraction level.

platsupport: Refactor TX2 timers to use 4k mapping

The TK1 and TX1 timers we use are all located within a 4k region.
However, on TX2 the timers are each on a separate 64k region. We need to
create multiple mappings to implement a logical timer because of this.
In the timer driver we also can't assume that the mapping is contiguous.

platsupport: Add initial TX2 support

The TX2 uses mostly the same default serial and timer devices. The
differences are:
- Extra interrupt routing for timers
- Different MMIO and interrupt mappings compared to TX1 and TK1

platsupport: Split nvidia definitions into plat

This is in preparation for the tx2 build which has the same devices but
with different interrupt and address mappings.

platsupport: TK1: Re-add support for periodic mode

This is being re-added in a way that doesn't break sel4test. Please refer to
the previous PR which was a revert PR.

platsupport: TK1 NVTMR: Revert design changes to the TK1 nvtmr backend

* During the course of doing the quadcopter, I had need to subtly change the way
the TK1's backend for the ltimer worked.
* This breaks seL4test.
* This reverts those changes

platsupport: TK1 NVTMR: Enable periodic mode support

nvidia_tmr: ack before starting the timer

stop any residual irqs

Remove pstimer from nvidia timers, refactor to suite ltimers

Fix whitespace

- remove trailing whitespace
- remove duplicate blank lines
- remove blank lines at end of file

fix licenses

libplatsupport: add tx1 platform

libplatsupport: create mach folder for nvidia machines