MAINTAINERS: thead: add git tree

Add git tree for T-Head device tree files and, in the future, drivers for
the T-Head TH1520 SoC.
Signed-off-by: Drew Fustini <drew@pdp7.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20240704180913.2516959-1-drew@pdp7.comSigned-off-by: Arnd Bergmann <arnd@arndb.de>

MAINTAINERS

@@ -19313,6 +19313,7 @@ F:	arch/riscv/boot/dts/
 X:	arch/riscv/boot/dts/allwinner/
 X:	arch/riscv/boot/dts/renesas/
 X:	arch/riscv/boot/dts/sophgo/
+X:	arch/riscv/boot/dts/thead/
 
 RISC-V PMU DRIVERS
 M:	Atish Patra <atishp@atishpatra.org>
@@ -19329,6 +19330,7 @@ M:	Guo Ren <guoren@kernel.org>
 M:	Fu Wei <wefu@redhat.com>
 L:	linux-riscv@lists.infradead.org
 S:	Maintained
+T:	git https://github.com/pdp7/linux.git
 F:	arch/riscv/boot/dts/thead/
 
 RNBD BLOCK DRIVERS