MAINTAINERS: git://github -> https://github.com for openrisc

Github deprecated the git:// links about a year ago, so let's move to
the https:// URLs instead.
Reported-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://github.blog/2021-09-01-improving-git-protocol-security-github/Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Stafford Horne <shorne@gmail.com>

MAINTAINERS

@@ -15240,7 +15240,7 @@ M:	Stafford Horne <shorne@gmail.com>
 L:	openrisc@lists.librecores.org
 S:	Maintained
 W:	http://openrisc.io
-T:	git git://github.com/openrisc/linux.git
+T:	git https://github.com/openrisc/linux.git
 F:	Documentation/devicetree/bindings/openrisc/
 F:	Documentation/openrisc/
 F:	arch/openrisc/