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/amlogic/axg/axg_pm.c b/plat/amlogic/axg/axg_pm.c
index e67f263..8a1b5d2 100644
--- a/plat/amlogic/axg/axg_pm.c
+++ b/plat/amlogic/axg/axg_pm.c
@@ -152,7 +152,7 @@
 	.pwr_domain_on			= axg_pwr_domain_on,
 	.pwr_domain_on_finish		= axg_pwr_domain_on_finish,
 	.pwr_domain_off			= axg_pwr_domain_off,
-	.pwr_domain_pwr_down_wfi	= axg_pwr_domain_pwr_down_wfi,
+	.pwr_domain_pwr_down		= axg_pwr_domain_pwr_down_wfi,
 	.system_off			= axg_system_off,
 	.system_reset			= axg_system_reset
 };