Move from strlen to strnlen_s.

Change-Id: I1d25a65e020b45b556723de14ef55a6140229dbb
diff --git a/inc/hf/arch/std.h b/inc/hf/arch/std.h
index b88e7d5..9fd3ec7 100644
--- a/inc/hf/arch/std.h
+++ b/inc/hf/arch/std.h
@@ -23,7 +23,6 @@
 
 int memcmp(const void *a, const void *b, size_t n);
 
-size_t strlen(const char *str);
 int strcmp(const char *a, const char *b);
 
 #define ctz(x) __builtin_ctz(x)
diff --git a/inc/hf/std.h b/inc/hf/std.h
index 101516e..356e61d 100644
--- a/inc/hf/std.h
+++ b/inc/hf/std.h
@@ -32,3 +32,5 @@
 void memset_s(void *dest, rsize_t destsz, int ch, rsize_t count);
 void memcpy_s(void *dest, rsize_t destsz, const void *src, rsize_t count);
 void memmove_s(void *dest, rsize_t destsz, const void *src, rsize_t count);
+
+size_t strnlen_s(const char *str, size_t strsz);