riscv: dts: thead: add clock to TH1520 gpio nodes

riscv: dts: thead: add clock to TH1520 gpio nodes

Add clock property to TH1520 gpio controller nodes. These clock gates
refer to corresponding enable bits in the peripheral clock gate control
register. Refer to register PERI_CLK_CFG in section 4.4.2.2.52 of the
TH1520 System User Manual.

Link: https://git.beagleboard.org/beaglev-ahead/beaglev-ahead/-/tree/main/docs
Signed-off-by: Drew Fustini <dfustini@tenstorrent.com>