intel: clear 'PLAT_SEC_ENTRY' in early platform setup

Ensure 'PLAT_SEC_ENTRY' is cleared during early platform
setup. This is to prevent the slave CPU cores jump to the stale
entry point after warm reset when using U-Boot SPL as first
stage boot loader.

Signed-off-by: Chee Hong Ang <chee.hong.ang@intel.com>
Change-Id: I3294ce2f74aa691d0cf311fa30f27f9d4fb8800a
3 files changed