chore(docs): drop the "wfi" from `pwr_domain_pwr_down_wfi`

To allow for generic handling of a wakeup, this hook is no longer
expected to call wfi itself. Update the name everywhere to reflect this
expectation so that future platform implementers don't get misled.

Change-Id: Ic33f0b6da74592ad6778fd802c2f0b85223af614
Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
diff --git a/plat/imx/imx8ulp/imx8ulp_psci.c b/plat/imx/imx8ulp/imx8ulp_psci.c
index 628acea..59af8be 100644
--- a/plat/imx/imx8ulp/imx8ulp_psci.c
+++ b/plat/imx/imx8ulp/imx8ulp_psci.c
@@ -538,7 +538,7 @@
 	.pwr_domain_suspend_finish = imx_domain_suspend_finish,
 	.get_sys_suspend_power_state = imx_get_sys_suspend_power_state,
 	.validate_power_state = imx_validate_power_state,
-	.pwr_domain_pwr_down_wfi = imx8ulp_pwr_domain_pwr_down_wfi,
+	.pwr_domain_pwr_down = imx8ulp_pwr_domain_pwr_down_wfi,
 };
 
 int plat_setup_psci_ops(uintptr_t sec_entrypoint,