acpi/ec: Add missing delays

Without these delays on fast systems like X230 the port is read before it's
updated.

Change-Id: I3e01fc348cc5170cec108a05095ba301055ed6b0
Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
Reviewed-on: http://review.coreboot.org/4617
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>
1 file changed