powerHAL: Hikey: Fix compilation warning

It's reporting the compilation warning as below:

device/linaro/hikey/power/power_hikey.c:447:32: warning: unused variable 'hikey' [-Wunused-variable]
    struct hikey_power_module *hikey = container_of(module,

This commit removes unused variable 'hikey' and add mark '__unused' for
parameter 'module'to dismiss the compilation warning.

Change-Id: I86ca979278dde7c959e9dc398def5078c8a59c5c
Signed-off-by: Leo Yan <leo.yan@linaro.org>
diff --git a/power/power_hikey.c b/power/power_hikey.c
index 2bcd296..34264d8 100644
--- a/power/power_hikey.c
+++ b/power/power_hikey.c
@@ -442,10 +442,9 @@
     pthread_mutex_unlock(&hikey->lock);
 }
 
-static void set_feature(struct power_module *module, feature_t feature, int state)
+static void set_feature(struct power_module __unused *module,
+                        feature_t feature, int state)
 {
-    struct hikey_power_module *hikey = container_of(module,
-                                              struct hikey_power_module, base);
     switch (feature) {
     default:
         ALOGW("Error setting the feature %d and state %d, it doesn't exist\n",