util: update hardware write protect check for flash_fp_mcu
util: update hardware write protect check for flash_fp_mcu

This method of checking seems more robust across devices. The old way
did not work on hatch.

BRANCH=none
BUG=b:124405913
TEST=make buildall -j
TEST=flash_fp_mcu /opt/google/biod/fw/nocturne_fp_v2.2.110-b936c0a3c.bin
TEST=flash_fp_mcu /opt/google/biod/fw/hatch_fp_v2.0.1359-6f54be08d.bin

Change-Id: I513f8bc5dafcdec7a95ac38657a342b3af509ccc
Signed-off-by: Tom Hughes <fc5c12f30a5ed2baa0581f44ee14ad1eb7b20d83@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1637584
Legacy-Commit-Queue: Commit Bot <5c2bf027dc5cc7ef186314391646e49f6866dc00@chromium.org>
Reviewed-by: Nicolas Boichat <f3daba1cdc403799935674d3cd4b0e5bd1804232@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec