MAINTAINERS: Add a git for the DT IDLE PM DOMAIN

Let' make it clear that we have git to manage the corresponding patches for
for the DT IDLE PM DOMAIN.

Cc: Rafael J. Wysocki <rafael@kernel.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20240404110018.568143-1-ulf.hansson@linaro.org

MAINTAINERS

@@ -5586,6 +5586,7 @@ CPUIDLE DRIVER - DT IDLE PM DOMAIN
 M:	Ulf Hansson <ulf.hansson@linaro.org>
 L:	linux-pm@vger.kernel.org
 S:	Supported
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/ulfh/linux-pm.git
 F:	drivers/cpuidle/dt_idle_genpd.c
 F:	drivers/cpuidle/dt_idle_genpd.h