riscv: defconfig: enable pinctrl and dwmac support for TH1520

Enable pinctrl and ethernet dwmac driver for the TH1520 SoC boards like
the BeagleV Ahead and the Sipeed LicheePi 4A.

Signed-off-by: Drew Fustini <drew@pdp7.com>
Reviewed-by: Emil Renner Berthing <emil.renner.berthing@canonical.com>
Link: https://lore.kernel.org/r/20241113184333.829716-1-drew@pdp7.com


Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>