hypfs: add ASSERT_UNREACHABLE() in hypfs_get_entry_rel()

The statement 'return ERR_PTR(-ENOENT);' on the final line of the
function 'hypfs_get_entry_rel()' is unreachable because the logic within
the infinite loop 'for (;;)' provides all possible exit paths for the
function. So there is no execution path to exit the loop and reach the
final that statement.

This unreachable code violates MISRA C Rule 2.1 which states: "A project
shall not contain unreachable code".

To fix that and potential compilers "control reaches end of non-void
function" warning, mark the code path as unreachable using macro
'ASSERT_UNREACHABLE()'.

Signed-off-by: Dmytro Prokopchuk <dmytro_prokopchuk1@epam.com>
Reviewed-by: Juergen Gross <jgross@suse.com>

xen/common/hypfs.c

@@ -348,6 +348,7 @@ static struct hypfs_entry *hypfs_get_entry_rel(struct hypfs_entry_dir *dir,
         dir = container_of(entry, struct hypfs_entry_dir, e);
     }
 
+    ASSERT_UNREACHABLE();
     return ERR_PTR(-ENOENT);
 }