Fixing the bug of CGPT when primary entry table is invalid.
This issue disclosed a bug of cgpt. The bug comes from the 'show' command always
reads the primary entry table when '-i partition' is specified. I added an
ANY_VALID constant for GetEntry to automatically select valid entry table.

Also fixed the bugs in cmd_boot.c and cmd_find.c. In cmd_add.c, stop user to
continue if any header/entry table is invalid.

Also fixed the bug that untrusted header size could cause segmentation failure.

Hungte, this is FYI. But welcome to do review.

TEST=RUNTESTS=1 emerge-x86-generic vboot_reference
     Manually tested:
       cgpt show /tmp/test -i 1 -b
       cgpt show /tmp/test
       cgpt add /tmp/test -i 1 -l TEST
       cgpt find /tmp/test -l STATE
       cgpt boot /tmp/test -i 1

Change-Id: Iaba9c635754096a82b3ec74634af184362d4e264
Change-Id: I6f3e87e3998457676e3388d2a6ed36c0564796d8

Review URL:
6 files changed