npcx: flash: Fix SR reg reads during UMA lock
npcx: flash: Fix SR reg reads during UMA lock

If UMA is locked, read and write access to SR* regs will fail, and we'll
be unable to determine or change our write protect state. Save our SR
regs before enabling UMA lock, and bring down UMA lock for a brief
period when writing SR regs.

BUG=chrome-os-partner:60029
BRANCH=gru
TEST=Manual on kevin with SW sync enabled.
flashrom -p ec --wp-enable -> verify success, check flags:
Flags:   wp_gpio_asserted ro_at_boot ro_now

Reboot host, check flags:
Flags:   wp_gpio_asserted ro_at_boot ro_now all_now

Verify flashrom -p ec --wp-status shows protected, and flashrom -p ec
--wp-disable fails.

Also verify same state after EC reset.

Boot into recovery mode, check flags:
Flags:   wp_gpio_asserted ro_at_boot ro_now

Remove WP screw, reboot EC, check flags:
Flags:   ro_at_boot ro_now

Verify flashrom WP status shows protected, and flashrom WP disable
succeeds and clears all flags.

Signed-off-by: Shawn Nematbakhsh <5259333ce42e3ace6a73988cec7115ed9d3a661a@chromium.org>
Change-Id: I17e32f7305600183e7fcb87f69a3feb88978f94e
Reviewed-on: https://chromium-review.googlesource.com/412977
(cherry picked from commit 6cfc0d0dd030b8b0334f99e99950a52fcf8267af)
Reviewed-on: https://chromium-review.googlesource.com/415497
Commit-Ready: Shawn N <5259333ce42e3ace6a73988cec7115ed9d3a661a@chromium.org>
Tested-by: Shawn N <5259333ce42e3ace6a73988cec7115ed9d3a661a@chromium.org>
Reviewed-by: Shawn N <5259333ce42e3ace6a73988cec7115ed9d3a661a@chromium.org>

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