stm32f0: Fix buffer size for i2c host command receive
stm32f0: Fix buffer size for i2c host command receive

Packets can be 128 bytes, and are preceded by a prefix byte.  So we
need a 129-byte buffer, not a 128-byte buffer.

BUG=chrome-os-partner:30079
BRANCH=none
TEST=do pd software sync; see that 128-byte packets transfer correctly

Change-Id: Ic1e6cfec2c042537768d1cd0eecea509cc90c052
Signed-off-by: Randall Spangler <62698fdbb84d1779579ee80c3f39fac22017e5bc@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/210502
Reviewed-by: Alec Berg <1a4429eeda29095a12e19a73405f80f5b7f37a63@chromium.org>

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