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/gxl/gxl_pm.c b/plat/amlogic/gxl/gxl_pm.c
index 433140b..5af4932 100644
--- a/plat/amlogic/gxl/gxl_pm.c
+++ b/plat/amlogic/gxl/gxl_pm.c
@@ -199,7 +199,7 @@
 	.pwr_domain_on			= gxl_pwr_domain_on,
 	.pwr_domain_on_finish		= gxl_pwr_domain_on_finish,
 	.pwr_domain_off			= gxl_pwr_domain_off,
-	.pwr_domain_pwr_down_wfi	= gxl_pwr_domain_pwr_down_wfi,
+	.pwr_domain_pwr_down		= gxl_pwr_domain_pwr_down_wfi,
 	.system_off			= gxl_system_off,
 	.system_reset			= gxl_system_reset,
 };