MAINTAINERS: Add a git for the ARM PSCI PM DOMAIN

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

Cc: Sudeep Holla <sudeep.holla@arm.com>
Cc: Rafael J. Wysocki <rafael@kernel.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20240404105952.562885-1-ulf.hansson@linaro.org

MAINTAINERS

@@ -5578,6 +5578,7 @@ M:	Ulf Hansson <ulf.hansson@linaro.org>
 L:	linux-pm@vger.kernel.org
 L:	linux-arm-kernel@lists.infradead.org (moderated for non-subscribers)
 S:	Supported
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/ulfh/linux-pm.git
 F:	drivers/cpuidle/cpuidle-psci-domain.c
 F:	drivers/cpuidle/cpuidle-psci.h