flash/nor/lpc2000: free allocated working area when target_write fails

In some circumstances (e.g. inappropriate jtag clock)
target_write_memory in lpc2000_iap_working_area_init might fail. The
allocated working area should be freed inside
lpc2000_iap_working_area_init in this error case.

This was leading to a weird segfault due to stack corruption later
when reset was executed.

Reported by quitte (Jonas Meyer).

Change-Id: Ia2ed42a9970a4d771727fd516a6eea88e9b859e2
Signed-off-by: Paul Fertser <fercerpav@gmail.com>
Reviewed-on: http://openocd.zylin.com/2696
Tested-by: jenkins

src/flash/nor/lpc2000.c

@@ -679,9 +679,11 @@ static int lpc2000_iap_working_area_init(struct flash_bank *bank, struct working
 	}
 
 	int retval = target_write_memory(target, (*iap_working_area)->address, 4, 2, jump_gate);
-	if (retval != ERROR_OK)
+	if (retval != ERROR_OK) {
 		LOG_ERROR("Write memory at address 0x%8.8" PRIx32 " failed (check work_area definition)",
 				(*iap_working_area)->address);
+		target_free_working_area(target, *iap_working_area);
+	}
 
 	return retval;
 }