iteflash: speed up flash (KGD) write
iteflash: speed up flash (KGD) write

This change saved about 65 seconds in writing (over I2C)
KGD 1M bytes part.

BUG=none
BRANCH=none
TEST=Programming IT81202 over I2C.

Change-Id: I84cc81dc16ceeabcfd15812a21a411ea660f2f7a
Signed-off-by: Dino Li <338d523ecf3700bd86eb9c34d220f91911d2a18c@ite.com.tw>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2391035
Reviewed-by: Jett Rink <9d4aef0593e6843318d99df31597fb6153b89787@chromium.org>

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