Initialize res in get_next_pcs_read_memory_unsigned_integer

This patch initialize res to zero, otherwise, it may have some garbage
bits after the *the_target->read_memory call.

gdb/gdbserver:

2016-05-05  Yao Qi  <yao.qi@linaro.org>

	* linux-arm-low.c (get_next_pcs_read_memory_unsigned_integer):
	Initialize res to zero.

gdb/gdbserver/ChangeLog

+2016-05-05  Yao Qi  <yao.qi@linaro.org>
+
+	* linux-arm-low.c (get_next_pcs_read_memory_unsigned_integer):
+	Initialize res to zero.
+
 2016-05-05  Yao Qi  <yao.qi@linaro.org>
 	* linux-arm-low.c (arm_sigreturn_next_pc): Change type of cpsr

gdb/gdbserver/linux-arm-low.c

@@ -262,6 +262,7 @@ get_next_pcs_read_memory_unsigned_integer (CORE_ADDR memaddr,
 {
   ULONGEST res;
 
+  res = 0;
   (*the_target->read_memory) (memaddr, (unsigned char *) &res, len);
   return res;
 }