add const to fix compiler warnings (#222)

loader/linux/icd_linux.c

diff --git a/loader/linux/icd_linux.c b/loader/linux/icd_linux.c
index 6dd2498..44915fe 100644
--- a/loader/linux/icd_linux.c
+++ b/loader/linux/icd_linux.c
@@ -132,7 +132,8 @@
     return strcoll(((struct dirElem *)a)->d_name, ((struct dirElem *)b)->d_name);
 }
 
-static inline void khrIcdOsDirEnumerate(char *path, char *env, const char *extension,
+static inline void khrIcdOsDirEnumerate(const char *path, const char *env,
+                                        const char *extension,
                                         khrIcdFileAdd addFunc, int bSort)
 {
     DIR *dir = NULL;