util/comm-i2c.c: Remove incorrect cast
util/comm-i2c.c: Remove incorrect cast

buf is type "uint8_t *", not "char *".

BRANCH=none
BUG=b:144959033
TEST=make buildall

Signed-off-by: Tom Hughes <fc5c12f30a5ed2baa0581f44ee14ad1eb7b20d83@chromium.org>
Change-Id: I0e813069f164b08324844009cd64d470b7d35405
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2864516
Reviewed-by: Jack Rosenthal <d3f605bef1867f59845d4ce6e4f83b8dc9e4e0ae@chromium.org>
Reviewed-by: Daisuke Nojiri <fd5f93af191bf7e8f73ea71cc3c0f66b41b1dd49@chromium.org>

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