libplatsupport,zynq: clarify code behavior

Signed-off-by: Axel Heider <axelheider@gmx.de>

libplatsupport,zynq: fix clearing isr bits

Signed-off-by: Axel Heider <axelheider@gmx.de>

libplatsupport,zynq: use proper constant

Signed-off-by: Axel Heider <axelheider@gmx.de>

libplatsupport: remove unused attribute

Signed-off-by: Axel Heider <axelheider@gmx.de>

trivial: style fix

Signed-off-by: Axel Heider <axelheider@gmx.de>

zynq: implement serial interrupt handler

The serial server expects the serial driver to handle the hardware
interrupts generated on a getchar event. Since the driver did not
implement this function, the hardware interrupt would never be handled,
which would contstantly trigger the serial server, even when no data had
been received.

zynq: toggle interrupts on serial rx and tx events

Since interrupts are enabled for the serial device, this follows the
programming guide found in Tables 21-8 and 21-9 of the ZUS+ TRM, which
suggests disabling interrupts before sending or receiving characters.

zynqmp: Don't set baud in serial driver init

The driver doesn't seem to have the correct clk frequency that it uses
to program the baud and this leads to incorrect baud settings. We assume
that the baud is already configured by the loaders that came before for
now.

platsupport/zynq: Added ps_cdev_static_init

Created a static initialisation function for the
zynq character device. This allows the user to pass in a
pre-mapped vaddr for the uart device.

platsupport/zynq: Refactored zynq serial init

Split up the zynq uart init implementation into multiple
functions. This makes the initialisation implementation more
modular for different serial initialisation functions.

Make zynq7000 names in zynq machine files more generic

Re-arrange Zynq7000 platform files to make a Zynq7000 machine