stm32f4: fix flash_physical_protect_now behavior

flash_physical_protect_now(), which is called when
EC_FLASH_PROTECT_ALL_NOW is set, should protect the entire flash
temporarily until reboot. Current behavior enable flash protect on all
region permanently. The correct implementation should be writing an
invalid key to the flash controller to disable flash flash only
temporarily until reboot.

Since the implementation of flash-stm32f3 and flash-stm32f4 is almost
the same after restoring the changes made in commit
35f4d8acaa40050f10158459a04e0bf9b24149c6, we merge to file by creating a
symlink from flash-stm32f3.c to flash-stm32f4.c to reduce code
duplication.

BRANCH=none
BUG=b:37584134
TEST=on eve:
     1) `ectool --name=cros_tp flashprotect`
        Flash protect flags: 0x00000008 wp_gpio_asserted
     2) `flashrom -p ec:type=tp --wp-enable
     3) `ectool --name=cros_tp reboot_ec`
     3) `flashrom -p ec:type=tp --wp-status`
        WP: status: 0x80
        WP: status.srp0: 1
        WP: write protect is enabled.
        WP: write protect range: start=0x00000000, len=0x00040000
     4) `ectool --name=cros_tp flashprotect`, all_now should present
        Flash protect flags: 0x0000000f wp_gpio_asserted ro_at_boot ro_now \
        all_now
     5) `ectool --name=cros_tp reboot_ec; sleep 0.3; \
         ectool --name=cros_tp rwsigaction abort` to stay in RO.
        In EC console, `flashinfo`, should show that only RO is actually
        flash protected:
        Protected now:
            YYYYYY..
     6) `flashrom -p ec:type=tp -w ec.bin -i EC_RW` works
     7) `make BOARD=ryu -j` works (for testing flash-stm32f3.c)

Change-Id: Ia7a60ae8b3084198abb468e4fc8074b4445d6915
Signed-off-by: Wei-Ning Huang <wnhuang@google.com>
Reviewed-on: https://chromium-review.googlesource.com/549681
Commit-Ready: Wei-Ning Huang <wnhuang@chromium.org>
Tested-by: Wei-Ning Huang <wnhuang@chromium.org>
Reviewed-by: Gwendal Grignou <gwendal@chromium.org>

0 files changed, 0 insertions, 0 deletions