soc/intel/common/block: Modify fast_spi_lock_bar function

Use 16bit write to avoid touching the upper two bytes that may cause
write cycle to fail in case a prior transaction has not completed.

This function sets the WRSDIS(Bit 11) and FLOCKDN (Bit 15) of the
SPIBAR + BIOS_HSFSTS_CTL. While WRSDIS is lockable with FLOCKDN,
writing both in the same cycle is guaranteed to work by design.

Avoid read->modify->write operation not to clear the RW1C bits
unintentionally.

Change-Id: Ia7880aaca0ed64150c994d49786a0a008bbaa98b
Signed-off-by: Barnali Sarkar <barnali.sarkar@intel.com>
Reviewed-on: https://review.coreboot.org/20643
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
2 files changed