kselftest: devices: Add of-fullname-regex property

Introduce a new 'of-fullname-regex' property that takes a regular
expression and matches against the OF_FULLNAME property. It allows
matching controllers that don't have a unique DT address across sibling
controllers, and thus dt-mmio can't be used.

One particular example of where this is needed is on MT8195 which has
multiple USB controllers described by two level deep nodes and using the
ranges property:

    ssusb2: usb@112a1000 {
        reg = <0 0x112a1000 0 0x2dff>, <0 0x112a3e00 0 0x0100>;
        ranges = <0 0 0 0x112a0000 0 0x3f00>;
        xhci2: usb@0 {

Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Link: https://lore.kernel.org/r/20240613-kselftest-discoverable-probe-mt8195-kci-v1-2-7b396a9b032d@collabora.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>