stm32f0: handle i2c reload mode properly
stm32f0: handle i2c reload mode properly

Fixed a bug that RELOAD bit not cleared properly when there's two
consecutive chip_i2c_xfer() calls, where the first call only contains
"write" transaction, and the second call contains a "read" transaction.

BUG=b:138095176
TEST=Case 1 - write and read in two separate i2c_xfer call:
              `ectool i2cxfer 1 0x55 8 0x64`
              On Krane, this should print the string "L16D2P31" in hex.
     Case 2 - no write and read 1 byte:
              `i2cscan` in ec console.
BRANCH=kukui

Change-Id: I57c1909058606b458801b3b35f54c16c1309c594
Signed-off-by: Ting Shen <c671d3efec3d7e7e285f3788bf0d1ba4c8605b78@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/1866222
Reviewed-by: Alexandru M Stan <1784cbba6d7675b1eba55eaefe41c7672ad9da3b@chromium.org>
Reviewed-by: Eric Yilun Lin <2f2733c7206ea2b76bd2db1905cc5e8a75841c48@chromium.org>
Commit-Queue: Ting Shen <c671d3efec3d7e7e285f3788bf0d1ba4c8605b78@chromium.org>
Tested-by: Ting Shen <c671d3efec3d7e7e285f3788bf0d1ba4c8605b78@chromium.org>

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