Zephyr: Allow big endian flag
Zephyr: Allow big endian flag

The flag for big endian i2c is handled in the upper layers of the
i2c_controller code, so it should be fine to silently ignore this flag
in the zephyr i2c logic.

BRANCH=None
BUG=b:195137794
TEST=zmake testall

Signed-off-by: Diana Z <cb2016afc7183e5356c690dc63b4ba817470501a@chromium.org>
Change-Id: Ic7e532a2890d526684fc47aca2e561a73ae90f10
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3340222
Reviewed-by: Jack Rosenthal <d3f605bef1867f59845d4ce6e4f83b8dc9e4e0ae@chromium.org>
Reviewed-by: Keith Short <f6d578f97033c25f1206cb57d52f358974c82954@chromium.org>

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