staging: mt7621-dts: use clock in pci phy nodes

staging: mt7621-dts: use clock in pci phy nodes

MT7621 SoC clock driver has already mainlined in
'commit 48df7a26f470 ("clk: ralink: add clock driver for mt7621 SoC")'
Hence we can use the clock in pcie phy nodes to
be able to get it from there in driver code.

Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Link: https://lore.kernel.org/r/20210514112820.32499-1-sergio.paracuellos@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>