Add crossystem fwupdate_tries and fix nv storage writes

Change-Id: I1835f4867de80aa3764e4a4c6d90b3fde2dc4308

R=reinauer@chromium.org
BUG=chromium_os:13672
TEST=manual

crossystem kern_nv=3
crossystem fwupdate_tries   # should print 3
crossystem fwupdate_tries=15
crossystem kern_nv          # should print 0x0000000F
crossystem kern_nv=0
crossystem fwupdate_tries   # should print 0

Review URL: http://codereview.chromium.org/6813056
diff --git a/utility/crossystem_main.c b/utility/crossystem_main.c
index 133ab00..0d44b99 100644
--- a/utility/crossystem_main.c
+++ b/utility/crossystem_main.c
@@ -62,6 +62,7 @@
   {"recovery_request", CAN_WRITE, "Recovery mode request (writable)"},
   {"dbg_reset", CAN_WRITE, "Debug reset mode request (writable)"},
   {"fwb_tries", CAN_WRITE, "Try firmware B count (writable)"},
+  {"fwupdate_tries", CAN_WRITE, "Times to try OS firmware update (writable)"},
   {"vbtest_errfunc", CAN_WRITE, "Verified boot test error function (writable)"},
   {"vbtest_errno", CAN_WRITE, "Verified boot test error number (writable)"},
   /* Fields not shown in a print-all list */