aboot: pmic: changes to avoid the compilation warnings

Fix for errors while enabling the Werror flag in LK.

Change-Id: I586d94225936d245889de81c7f90e269ef0863f9
diff --git a/dev/pmic/pm8x41/pm8x41.c b/dev/pmic/pm8x41/pm8x41.c
index 9315f72..328d21d 100644
--- a/dev/pmic/pm8x41/pm8x41.c
+++ b/dev/pmic/pm8x41/pm8x41.c
@@ -37,11 +37,10 @@
 
 static uint8_t mpp_slave_id;
 
-uint8_t pmi8994_config_mpp_slave_id(uint8_t slave_id)
+void pmi8994_config_mpp_slave_id(uint8_t slave_id)
 {
 	mpp_slave_id = slave_id;
 }
-
 /* SPMI helper functions */
 uint8_t pm8x41_reg_read(uint32_t addr)
 {