[PATCH] symbols: fix xensyms_read() hitting the final "end" symbol

[Jan Beulich]

A new "no (more) symbol" path there was lacking a necessary unlock.

Fixes: d3b637fba31b ("symbols: arrange to know where functions end")
Coverity ID: 1665212
Signed-off-by: Jan Beulich <jbeul...@suse.com>

--- a/xen/common/symbols.c
+++ b/xen/common/symbols.c
@@ -202,7 +202,10 @@ int xensyms_read(uint32_t *symnum, char
     {
         ++next_offset;
         if ( ++*symnum == symbols_num_addrs )
+        {
+            spin_unlock(&symbols_mutex);
             goto no_symbol;
+        }
     }
 
     *type = symbols_get_symbol_type(next_offset);