fm_hci_api.h: Resolve -Wwritable-strings warnings in fm_hci FW library variables

* fixes: ISO C++11 does not allow conversion from string literal to 'char *'

Change-Id: I84dd01eb8a0b4035d5708b126b6b1f074e698251
Signed-off-by: micky387 <mickaelsaibi@free.fr>
diff --git a/fm_hci/fm_hci_api.h b/fm_hci/fm_hci_api.h
index 1602fbb..3a11b33 100644
--- a/fm_hci/fm_hci_api.h
+++ b/fm_hci/fm_hci_api.h
@@ -42,7 +42,7 @@
     FM_HC_STATUS_NULL_POINTER,
 } fm_hc_status_t;
 
-static char *status_s[] = {
+const static char *status_s[] = {
     "Success",
     "Failed, generic error",
     "Not ready",
@@ -52,7 +52,7 @@
     "NULL pointer dereference",
 };
 
-static inline char *fm_hci_status(int status) {
+const static inline char *fm_hci_status(int status) {
     return status_s[status];
 }