staging: mt7621-pci: parse some dt properties from root port child nodes

staging: mt7621-pci: parse some dt properties from root port child nodes

Properties 'clocks', 'resets' and 'phys' have been moved from parent
node to the root port children. Hence we have to adapt the way device
tree is parsed in driver code to properly align things and make all
the stuff work.
Note that we moved from using 'devm_reset_control_get_exclusive() to
'of_reset_control_get_exclusive()' so we need to properly call the
'reset_control_put()' function manually in error and remove paths.

Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Link: https://lore.kernel.org/r/20210607120153.24989-6-sergio.paracuellos@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>