Remove the byte order parameter to target_read_string

target_read_string takes a byte order parameter, but only uses this to
check whether a given character is zero.  This is readily done without
requiring the parameter, so remove it.

gdb/c-lang.c

@@ -353,7 +353,7 @@ c_get_string (struct value *value, gdb::unique_xmalloc_ptr<gdb_byte> *buffer,
 	fetchlimit = UINT_MAX;
 
       err = target_read_string (addr, *length, width, fetchlimit,
-				byte_order, buffer, length);
+				buffer, length);
       if (err != 0)
 	memory_error (TARGET_XFER_E_IO, addr);
     }