Allow repeated waitms commands without resetting
Allow repeated waitms commands without resetting

At present issuing several 'waitms 1000' commands immediately after each
other trips the watchdog. Add a watchdog reload to avoid this.

Also document the behaviour in the command help.

BUG=b:72542719
BRANCH=none
TEST=manually on grunt, pasting these three lines in:
  waitms 1000
  waitms 1000
  waitms 1000
and see that it does not reset now.
Change-Id: I453708299e4e26c1bbdb5fc406f26e916e7389af
Signed-off-by: Simon Glass <c00b0378376498bd9cd974c388df8854c0131d27@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/955927
Reviewed-by: Edward Hill <db1406b34e091703092b6b136bdfeb2c8125fc0e@chromium.org>
Reviewed-by: Martin Roth <79230511ccf79da3f7e9e82dbcc9c1ec2f734fa0@chromium.org>

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