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/nxp/common/psci/plat_psci.c b/plat/nxp/common/psci/plat_psci.c
index f6dd7b3..c154a7f 100644
--- a/plat/nxp/common/psci/plat_psci.c
+++ b/plat/nxp/common/psci/plat_psci.c
@@ -433,7 +433,7 @@
 	.pwr_domain_off	= _pwr_domain_off,
 #endif
 #if (SOC_CORE_OFF || SOC_CORE_PWR_DWN)
-	.pwr_domain_pwr_down_wfi = _pwr_down_wfi,
+	.pwr_domain_pwr_down = _pwr_down_wfi,
 #endif
 #if (SOC_CORE_STANDBY || SOC_CORE_PWR_DWN)
 	 /* cpu_suspend */