Fix build bug in ppc-linux-nat.c

The buildbot pointed out that my value refactoring series introduced a
bug in ppc-linux-nat.c:

../../binutils-gdb/gdb/ppc-linux-nat.c: In member function ‘int ppc_linux_nat_target::num_memory_accesses(const std::vector<gdb::ref_ptr<value, value_ref_policy> >&)’:
../../binutils-gdb/gdb/ppc-linux-nat.c:2458:44: error: expected unqualified-id before ‘->’ token
 2458 |       if (VALUE_LVAL (v) == not_lval || v->->deprecated_modifiable () == 0)

I don't know how that happened, but I am checking in this patch which
I think should fix it.  It just removes the second "->".

I can't readily test this, so perhaps there's another bug lurking
after this one.

gdb/ppc-linux-nat.c

diff --git a/gdb/ppc-linux-nat.c b/gdb/ppc-linux-nat.c
index e4fcce6..32c0177 100644
--- a/gdb/ppc-linux-nat.c
+++ b/gdb/ppc-linux-nat.c
@@ -2455,7 +2455,7 @@ ppc_linux_nat_target::num_memory_accesses (const std::vector<value_ref_ptr>
       struct value *v = iter.get ();
 
       /* Constants and values from the history are fine.  */
-      if (v->lval () == not_lval || v->->deprecated_modifiable () == 0)
+      if (v->lval () == not_lval || v->deprecated_modifiable () == 0)
 	continue;
       else if (v->lval () == lval_memory)
 	{