staging: mt7621-pci-phy: dt: bindings: remove bindings txt file

Yaml file for bindings has been properly added. Hence, remove
the old txt file.

Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Link: https://lore.kernel.org/r/20200410091836.13068-3-sergio.paracuellos@gmail.com


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